# Sum of all integers from 1 to n

I'm honestly surprised that this hasn't been done already. If you can find an existing thread, by all means mark this as a duplicate or let me know.

# Input

Your input is in the form of any positive integer greater than or equal to 1.

# Output

You must output the sum of all integers between and including 1 and the number input.

# Example

 In: 5
1+2+3+4+5 = 15
Out: 15


OEIS A000217 — Triangular numbers: a(n) = binomial(n+1,2) = n(n+1)/2 = 0 + 1 + 2 + ... + n.

Run the code snippet below to view a leaderboard for this question's answers. (Thanks to programmer5000 and steenbergh for suggesting this, and Martin Ender for creating it.)

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• Closely related Jul 18, 2017 at 20:36
• @FryAmTheEggman Sorry - had a bit of a brain fart there. I see what you mean. Jul 18, 2017 at 20:45
• @Aaron you got ninja'd by Husk, which was just posted with a 1 byte solution Jul 18, 2017 at 21:35
• I suggest a stack snippet.
– user58826
Jul 19, 2017 at 11:42
• Jul 27, 2017 at 12:20

# MMIX, 28 bytes (7 instructions)

(a function)

23FF0001 1A0000FF 3F000001 FEFF0003
3BFFFF3F C00000FF F8010000


Dissassembly:

    ADDU $255,$0,1      // tmp = n + 1
MULU $0,$0,$255 // rH:n = n * tmp SRU$0,$0,1 // n >>>= 1 GET$255,rH        // tmp = rH
SLU  $255,$255,63   // tmp <<= 63
OR   $0,$0,$255 // n |= tmp POP 1,0 // return(n)  I used the obvious straight-line version. This computes the result mod $$\2^{64}\$$. # JavaScript (Node.js), 12 bytes n=>(n*n+n)/2  Try it online! • -2 bytes: n=>n*--n/2 Jul 19, 2017 at 17:28 • Could you elaborate? :-) Jul 19, 2017 at 18:19 • n=>n*++n/2 is the same thing as n=>n*(n+1)/2, while also changing the value of n. Since we don't need n anymore, this doesn't matter. (n=>n*--n/2 is incorrect due to a typo) Jul 20, 2017 at 7:40 # Ruby, 24 bytes n=gets.to_i;p n*(n+1)//2 Direct Attempt This Online! # Ruby, 24 bytes n=gets.to_i;p (1..n).sum The same as previous, but using sum. Attempt This Online! # Fig, $$\2\log_{256}(96)\approx\$$ 1.646 bytes Sa  See the README to see how to run this Sa # Takes a number as input S # Sum a # Of the range [1, n]  # Chocolate, 1 byte ∑  Try it online! # Knight, 11 bytes O/*+1=xPx 2  Try it online! # Arturo, 12 bytes $=>[∑1..&]


Try it

# ARBLE, 15 bytes

sum(range(1,n))


Try it online!

## Binary-encoded Golfical, 17 bytes

Hexdump of binary encoding:

00 90 01 15 0c 01 04 01 3c 0e 01 00
02 0a 01 3d 17


The encoded version can be converted to a runnable program image using the encoder utility included in the language's github repository, or run directly by using the -x flag

Original program image:

Magnified 45x with RGB colors labeled:

# Alice, 11 bytes

/O
\I@/rd&+


Try it online!

/I\rd&+/O@   Full program flatened
/I\          Reads the input and push it on the stack
r         Pops, Create a range from 0 to the input on the stack
d        Pushes on the depth of the stack on the stack
Flow control instructions
&+      Pops sum all the numbers in the stack
/O@   Prints and exit


# Desmoslang Assembly, 11 Bytes

IS*.5(D+1OT

# ARM Thumb machine code, 8 bytes

0:  1c41  adds  r1, r0, #1  @  n + 1
2:  4348  muls  r0, r1      @  * n
4:  0840  lsrs  r0, r0, #1  @  / 2
6:  4770  bx    lr