A087914 Numbers m such that A007947(m) = A007947(k) and A007947(m+1) = A007947(k+1), for some k < m.

8, 48, 224, 960, 1215, 3968, 16128, 65024, 261120, 1046528, 4190208, 16769024, 67092480, 268402688, 1073676288, 4294836224

Offset

1,1

Comments

For every k > 1, the sequence includes 4^k - 2^(k+1), with m = 2^k - 2. - David Wasserman, Jan 29 2004

a(12) <= 16769024. a(13) <= 67092480. a(14) <= 268402688. a(15) <= 1073676288. [Donovan Johnson, Dec 19 2008]

Links

Table of n, a(n) for n=1..16.

Example

A007947(8) = A007947(2) and A007947(9) = A007947(3), so 8 is in the sequence.

Prog

(PARI) rad(n) = factorback(factorint(n)[, 1]); \\ A007947
isok(m) = {my(rm = rad(m), sm = rad(m+1)); for (k=1, m-1, if ((rad(k) == rm) && (rad(k+1) == sm), return (1)); ); } \\ Michel Marcus, Apr 05 2021

Crossrefs

Cf. A007947, A088966.

Sequence in context: A093199 A263507 A261975 * A271061 A211012 A081084

Adjacent sequences: A087911 A087912 A087913 * A087915 A087916 A087917

Keyword

nonn,hard,more

Author

Naohiro Nomoto, Oct 26 2003

Extensions

a(7)-a(11) from Donovan Johnson, Dec 19 2008

Name edited by Michel Marcus, Apr 06 2021

Confirmed a(12)-a(15) and extended with a(16) by Martin Ehrenstein, Apr 18 2021

Status

approved