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A295391 a(1) = 2; a(n+1) = 1 + (a(n)^2 - a(n))*(1+1/n) for n >= 1. 1
2, 5, 31, 1241, 1923551, 4440055831261, 22999778415495431257188671, 604559779613588034852176053517136070371409409780081, 411179093017233901729922229390651516928263091167446329166300037456998815010841080003014976133796409791 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

(a(1), ..., a(n-1), a(n)-1) is an integer solution to the equation Sum_{k=1}^n k/x(k) = 1.

LINKS

Robert Israel, Table of n, a(n) for n = 1..12

R. Israel, Set of solutions to a sum, Mathematics StackExchange.

EXAMPLE

1/1 = 1.

1/2 + 2/4 = 1.

1/2 + 2/5 + 3/30 = 1.

1/2 + 2/5 + 3/31 + 4/1240 = 1.

1/2 + 2/5 + 3/31 + 4/1241 + 5/1923550 = 1.

MAPLE

a[1]:= 2:

for n from 1 to 10 do a[n+1]:= 1 + (a[n]^2 - a[n])*(1+1/n) od:

seq(a[i], i=1..11);

MATHEMATICA

Fold[Append[#1, 1 + (Last[#1]^2 - Last[#1]) (1 + 1/#2)] &, {2}, Range@ 8] (* Michael De Vlieger, Nov 21 2017 *)

CROSSREFS

Sequence in context: A051399 A080582 A064845 * A259644 A132527 A182327

Adjacent sequences:  A295388 A295389 A295390 * A295392 A295393 A295394

KEYWORD

nonn

AUTHOR

Robert Israel, Nov 21 2017

STATUS

approved

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Last modified March 18 17:51 EDT 2019. Contains 321292 sequences. (Running on oeis4.)