A014865 Numbers k that divide s(k), where s(1)=1, s(j)=15*s(j-1)+j.

1, 3, 5, 7, 15, 21, 35, 49, 55, 105, 147, 165, 245, 343, 385, 605, 723, 735, 903, 915, 1029, 1155, 1715, 1815, 2401, 2485, 2695, 3615, 3685, 4235, 4515, 5061, 5145, 6321, 6405, 6655, 7203, 7455, 8085, 10065, 11055, 12005, 12705, 16807, 17395

Offset

1,2

Comments

Conjecture: all terms are odd, all terms greater than 7 are composite, and all terms greater than 1 are divisible by 3 or 5 or 7 some combination therof. - Harvey P. Dale, Dec 04 2020

Links

Harvey P. Dale, Table of n, a(n) for n = 1..100

Mathematica

nxt[{n_, a_}]:={n+1, 15a+n+1}; Select[NestList[nxt, {1, 1}, 17500], Divisible[ #[[2]], #[[1]]]&][[All, 1]] (* Harvey P. Dale, Dec 04 2020 *)

Crossrefs

Sequence in context: A029466 A014872 A018501 * A018617 A018286 A194360

Adjacent sequences: A014862 A014863 A014864 * A014866 A014867 A014868

Keyword

nonn

Author

N. J. A. Sloane, Olivier Gérard

Status

approved