A356425 - OEIS

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A356425

Sum of divisors of numbers of least prime signature: a(n) = A000203(A025487(n)).

1, 3, 7, 12, 15, 28, 31, 60, 72, 63, 91, 124, 168, 127, 195, 252, 360, 255, 403, 546, 508, 576, 600, 744, 511, 819, 1170, 1020, 1344, 1240, 1512, 1023, 1651, 2418, 2044, 2880, 2520, 2821, 3048, 2047, 3600, 3315, 4368, 3751, 4914, 4092, 5952, 5080, 6045, 6120

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OFFSET

1,2

COMMENTS

This sequence is to A146288 as sigma (A000203, the sum of divisors function) is to tau (A000005, the number of divisors function).

LINKS

Hal M. Switkay, Table of n, a(n) for n = 1..67

MATHEMATICA

s = {1}; Do[If[GreaterEqual @@ (f = FactorInteger[n])[[;; , 2]] && PrimePi[f[[-1, 1]]] == Length[f], AppendTo[s, DivisorSigma[1, n]]], {n, 2, 2000}]; s (* Amiram Eldar, Dec 12 2022 *)

CROSSREFS

Cf. A000005, A000203, A025487, A146288.

Sequence in context: A033015 A225574 A317305 * A096998 A356353 A317307

Adjacent sequences: A356422 A356423 A356424 * A356426 A356427 A356428

KEYWORD

nonn

AUTHOR

Hal M. Switkay, Dec 11 2022

STATUS

approved