Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #13 Mar 09 2023 15:34:25
%S 14,42,70,78,84,98,112,114,124,126,154,156,168,182,186,198,210,222,
%T 228,234,238,252,258,266,294,308,310,312,322,336,342,350,366,372,378,
%U 390,396,402,406,418,420,434,438,444,456,462,468,474,490,504,516,518,532,546,550,558
%N Even numbers k such that k^2 is not in A014567; complement of A356448 in the even numbers.
%C Even numbers k such that k and sigma(k^2) are not coprime, sigma = A000203.
%H Jianing Song, <a href="/A356452/b356452.txt">Table of n, a(n) for n = 1..12241</a> (all terms <= 80000)
%F a(n) = 2*A356454(n).
%e 14 is a term since 14 and sigma(14^2) = 399 have a common factor 7.
%t Select[2 Range[300],!CoprimeQ[#,DivisorSigma[1,#^2]]&] (* _Harvey P. Dale_, Mar 09 2023 *)
%o (PARI) isA356452(n) = !(n%2) && gcd(n, sigma(n^2))>1
%Y Cf. A014567, A000203, A356448, A356453, A356454.
%K nonn,easy
%O 1,1
%A _Jianing Song_, Aug 07 2022