A304207 a(1)=17; for n>1, a(n) = (a(n-1)^2 - 1)/2 if n is even, a(n-1) + 1 if n is odd.

17, 144, 145, 10512, 10513, 55261584, 55261585, 1526921388356112, 1526921388356113, 1165744463109679828308252234384, 1165744463109679828308252234385, 679480076635437837059150531810555804350472205781672488164112, 679480076635437837059150531810555804350472205781672488164113

Offset

1,1

Comments

{17, 144, 145}, {145, 10512, 10513}, {10513, 55261584, 55261585}, ... are sides {a < b < c} of the right triangles, with hypotenuse c = b + 1.

Links

Eric Chen, Table of n, a(n) for n = 1..21

Mathematica

nxt[{n_, a_}]:={n+1, If[OddQ[n], (a^2-1)/2, a+1]}; NestList[nxt, {1, 17}, 20][[All, 2]] (* Harvey P. Dale, Mar 27 2021 *)

Prog

(PARI) a(n) = if(n==1, 17, if(n%2, a(n-1)+1, (a(n-1)^2 - 1)/2)) \\ Eric Chen, Jun 09 2018

Crossrefs

Same basic form as A076601, A076602, A076603, and A076604.

Sequence in context: A222478 A228254 A376459 * A163038 A216422 A008417

Adjacent sequences: A304204 A304205 A304206 * A304208 A304209 A304210

Keyword

nonn

Author

Benjamin Knight, May 08 2018

Status

approved