A068334 a(1) = 1; a(n+1) = 1 + Product_{k|n} a(k), product is over the positive divisors, k, of n.

1, 2, 3, 4, 9, 10, 61, 62, 497, 1492, 26857, 26858, 6445921, 6445922, 786402485, 21232867096, 10531502079617, 10531502079618, 314049392014208761, 314049392014208762, 33736441887734362049089, 6173768865455388254983288

Offset

1,2

Links

Seiichi Manyama, Table of n, a(n) for n = 1..66

Example

a(7) = 1 + a(1)*a(2)*a(3)*a(6) = 1 + 1*2*3*10 = 61.

Mathematica

Nest[Append[#1, 1 + Times @@ #1[[Divisors[#2] ]] ] & @@ {#, Length[#]} &, {1}, 21] (* Michael De Vlieger, Apr 13 2021 *)

Prog

(PARI) lista(nn) = {my(va = vector(nn)); va[1] = 1; for (n=2, nn, my(d=divisors(n-1)); va[n] = 1 + prod(k=1, #d, va[d[k]]); ); va; } \\ Michel Marcus, Apr 13 2021

Crossrefs

Cf. A068336, A343390.

Sequence in context: A291163 A180743 A162662 * A283874 A263092 A118223

Adjacent sequences: A068331 A068332 A068333 * A068335 A068336 A068337

Keyword

nonn

Author

Leroy Quet, Feb 27 2002

Status

approved