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A111631 Inverse of A110412 or zero if none exists. 0

%I

%S 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,

%T 65,44,626,52,32,50,125,91,24,221,404,212,42,81,45,63,40,75,66,36,56,

%U 64,338,88,104,130,153,154,152,190,328,175,48,184,245,286,182,100,105,243

%N Inverse of A110412 or zero if none exists.

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

%C Found zeros < 7500 only for 12 & 20.

%t 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}]

%Y Cf. A110412.

%K nonn

%O 0,2

%A _Amarnath Murthy_ and _Robert G. Wilson v_, Aug 09 2005

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Last modified January 27 13:45 EST 2022. Contains 350607 sequences. (Running on oeis4.)