A356452 - OEIS

A356452

Even numbers k such that k^2 is not in A014567; complement of A356448 in the even numbers.

14, 42, 70, 78, 84, 98, 112, 114, 124, 126, 154, 156, 168, 182, 186, 198, 210, 222, 228, 234, 238, 252, 258, 266, 294, 308, 310, 312, 322, 336, 342, 350, 366, 372, 378, 390, 396, 402, 406, 418, 420, 434, 438, 444, 456, 462, 468, 474, 490, 504, 516, 518, 532, 546, 550, 558

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OFFSET

1,1

COMMENTS

Even numbers k such that k and sigma(k^2) are not coprime, sigma = A000203.

LINKS

Jianing Song, Table of n, a(n) for n = 1..12241 (all terms <= 80000)

FORMULA

a(n) = 2*A356454(n).

EXAMPLE

14 is a term since 14 and sigma(14^2) = 399 have a common factor 7.

MATHEMATICA

Select[2 Range[300], !CoprimeQ[#, DivisorSigma[1, #^2]]&] (* Harvey P. Dale, Mar 09 2023 *)

PROG

(PARI) isA356452(n) = !(n%2) && gcd(n, sigma(n^2))>1

CROSSREFS

Cf. A014567, A000203, A356448, A356453, A356454.

Sequence in context: A208360 A208359 A245629 * A163756 A005587 A244101

Adjacent sequences: A356449 A356450 A356451 * A356453 A356454 A356455

KEYWORD

nonn,easy

AUTHOR

Jianing Song, Aug 07 2022

STATUS

approved