A351538 - OEIS

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A351538

Numbers k such that both k and sigma(k) are congruent to 2 modulo 4 and the 3-adic valuation of sigma(k) is exactly 1.

26, 74, 122, 146, 194, 218, 234, 314, 362, 386, 458, 482, 554, 626, 650, 666, 674, 698, 746, 794, 818, 842, 866, 914, 1082, 1098, 1154, 1202, 1226, 1314, 1322, 1346, 1418, 1466, 1514, 1538, 1658, 1706, 1746, 1754, 1850, 1874, 1962, 1994, 2018, 2042, 2066, 2106, 2138, 2186, 2234, 2258, 2306, 2402, 2426, 2474, 2498

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OFFSET

1,1

COMMENTS

All the terms of the form 4u+2 in A349745 (if they exist) are found in this sequence. As A351537 is the intersection of A191218 and A329963, and the latter has asymptotic density zero, so has this sequence also. It is conjectured that A351555(a(n)) is nonzero for all n, which would imply that the intersection with A349745 is empty. - Antti Karttunen, Feb 19 2022

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..25000

Index entries for sequences related to sigma(n)

FORMULA

a(n) = 2 * A351537(n).

PROG

(PARI) isA351538(n) = if(!(2==(n%4)), 0, my(s=sigma(n)); (2 == (s%4)) && (1==valuation(s, 3)));

CROSSREFS

Cf. A191218, A329963, A349745, A351537.

Probably a subsequence of A351543. (See also A351550, A351555).

Sequence in context: A039377 A043200 A043980 * A065302 A353635 A044164

Adjacent sequences: A351535 A351536 A351537 * A351539 A351540 A351541

KEYWORD

nonn

AUTHOR

Antti Karttunen, Feb 14 2022

STATUS

approved