A343226 - OEIS

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A343226

a(n) = gcd(sigma(n), n+A003415(n)), where A003415 is the arithmetic derivative, and sigma is the sum of divisors of n.

5

1, 3, 4, 1, 6, 1, 8, 5, 1, 1, 12, 28, 14, 1, 1, 1, 18, 39, 20, 2, 1, 1, 24, 4, 1, 1, 2, 4, 30, 1, 32, 7, 1, 1, 1, 1, 38, 1, 1, 18, 42, 1, 44, 4, 6, 1, 48, 4, 3, 1, 1, 2, 54, 15, 1, 4, 1, 1, 60, 8, 62, 1, 2, 1, 1, 1, 68, 14, 1, 3, 72, 3, 74, 1, 2, 4, 1, 1, 80, 2, 1, 1, 84, 16, 1, 1, 1, 12, 90, 3, 1, 4, 1, 1, 1, 4

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OFFSET

1,2

COMMENTS

a(n) = n+1 iff n is prime (A000040). - Bernard Schott, Jun 01 2021

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..20000

Index entries for sequences related to sigma(n)

FORMULA

a(n) = gcd(A000203(n), A129283(n)) = gcd(A000203(n), A211991(n)).

a(n) = A000203(n) / A343227(n).

a(n) = 1 if n is squarefree semiprime (A006881). - Bernard Schott, Jun 02 2021

PROG

(PARI)

A003415(n) = if(n<=1, 0, my(f=factor(n)); n*sum(i=1, #f~, f[i, 2]/f[i, 1]));

A129283(n) = (n+A003415(n));

A343226(n) = gcd(sigma(n), A129283(n));

CROSSREFS

Cf. A000203, A003415, A129283, A211991, A343227.

Sequence in context: A339964 A342915 A276433 * A030707 A349629 A254525

Adjacent sequences: A343223 A343224 A343225 * A343227 A343228 A343229

KEYWORD

nonn

AUTHOR

Antti Karttunen, Apr 15 2021

STATUS

approved