A111631 Inverse of A110412 or zero if none exists.

1, 2, 3, 5, 4, 17, 13, 6, 9, 8, 14, 0, 22, 26, 15, 401, 21, 12, 16, 0, 18, 20, 77, 226, 28, 65, 44, 626, 52, 32, 50, 125, 91, 24, 221, 404, 212, 42, 81, 45, 63, 40, 75, 66, 36, 56, 64, 338, 88, 104, 130, 153, 154, 152, 190, 328, 175, 48, 184, 245, 286, 182, 100, 105, 243

Offset

0,2

Comments

A110412: Sum_{d<n is a divisor of n} tau(n-d).

Found zeros < 7500 only for 12 & 20.

Links

Table of n, a(n) for n=0..64.

Mathematica

f[n_] := Plus @@ (DivisorSigma[0, n - # ] & /@ Most[Divisors[n]]); t = Table[0, {100}]; Do[a = f[n]; If[a < 100 && t[[a + 1]] == 0, t[[a + 1]] = n; Print[{a, n}]], {n, 630}]

Crossrefs

Cf. A110412.

Sequence in context: A119745 A095753 A139537 * A235610 A118141 A343767

Adjacent sequences: A111628 A111629 A111630 * A111632 A111633 A111634

Keyword

nonn

Author

Amarnath Murthy and Robert G. Wilson v, Aug 09 2005

Status

approved