A061496 - OEIS

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A061496

a(n) = gcd(abundant(n), abundant(n+1)) where abundant(n) is the n-th abundant number.

6, 2, 4, 6, 6, 4, 2, 6, 6, 2, 4, 6, 2, 2, 6, 2, 4, 4, 2, 6, 4, 2, 2, 4, 4, 2, 6, 6, 6, 6, 2, 4, 6, 6, 4, 2, 6, 6, 2, 4, 6, 6, 4, 2, 2, 4, 4, 2, 6, 4, 2, 2, 4, 6, 6, 6, 6, 6, 2, 4, 6, 2, 4, 4, 2, 6, 6, 6, 4, 2, 2, 4, 6, 2, 4, 6, 6, 4, 2, 6, 2, 2, 2, 6, 4, 2, 2

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

The first occurrence of 1, 2, 3, 4, 5 and 6 is at n = 1432, 2, 231, 3, 1335014838 and 1, respectively. There are no terms larger than 6. - Amiram Eldar, Feb 22 2023

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from Harry J. Smith)

FORMULA

a(n) = gcd(A005101(n), A005101(n+1)).

EXAMPLE

a(1) = gcd(12, 18) = 6.

MATHEMATICA

GCD @@@ Partition[Select[Range[400], DivisorSigma[-1, #] > 2 &], 2, 1] (* Amiram Eldar, Feb 22 2023 *)

PROG

(PARI) { x=12; for (n=1, 1000, y=x+1; until (sigma(y) > 2*y, y++); write("b061496.txt", n, " ", gcd(x, y)); x=y ) } \\ Harry J. Smith, Jul 23 2009

CROSSREFS

Cf. A005101.

Sequence in context: A010493 A375068 A175286 * A125115 A202244 A257535

Adjacent sequences: A061493 A061494 A061495 * A061497 A061498 A061499

KEYWORD

nonn

AUTHOR

Jason Earls, Jun 12 2001

EXTENSIONS

Corrected and extended by Jason G. Wurtzel, Nov 21 2006

More terms from Sean A. Irvine, Feb 18 2023

STATUS

approved