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A341523 Number of prime factors (with multiplicity) shared by n and sigma(n): a(n) = bigomega(gcd(n, sigma(n))). 4
0, 0, 0, 0, 0, 2, 0, 0, 0, 1, 0, 2, 0, 1, 1, 0, 0, 1, 0, 1, 0, 1, 0, 3, 0, 1, 0, 3, 0, 2, 0, 0, 1, 1, 0, 0, 0, 1, 0, 2, 0, 2, 0, 2, 1, 1, 0, 2, 0, 0, 1, 1, 0, 2, 0, 3, 0, 1, 0, 3, 0, 1, 0, 0, 0, 2, 0, 1, 1, 1, 0, 1, 0, 1, 0, 2, 0, 2, 0, 1, 0, 1, 0, 3, 0, 1, 1, 2, 0, 3, 1, 2, 0, 1, 1, 3, 0, 0, 1, 0, 0, 2, 0, 1, 1 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,6

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..65537

Index entries for sequences related to sigma(n)

FORMULA

a(n) = A001222(A009194(n)).

a(n) = A001222(n) - A341524(n).

a(A003961(n)) = A341519(n).

MATHEMATICA

Table[PrimeOmega[GCD[n, DivisorSigma[1, n]]], {n, 1, 100}] (* Amiram Eldar, Feb 17 2021 *)

PROG

(PARI) A341523(n) = bigomega(gcd(n, sigma(n)));

CROSSREFS

Cf. A000203, A003961, A009194, A014567 (positions of zeros), A341519, A341524.

Sequence in context: A070201 A070138 A024153 * A079127 A056674 A336107

Adjacent sequences:  A341520 A341521 A341522 * A341524 A341525 A341526

KEYWORD

nonn

AUTHOR

Antti Karttunen, Feb 17 2021

STATUS

approved

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Last modified April 10 11:15 EDT 2021. Contains 342845 sequences. (Running on oeis4.)