A351095 - OEIS

%I #7 Feb 03 2022 16:45:10

%S 35,57,65,93,145,177,205,209,217,219,237,289,303,305,323,377,393,413,

%T 415,427,453,473,485,497,515,517,529,533,537,553,597,629,681,697,699,

%U 713,749,781,785,793,817,835,849,869,895,917,933,965,989,1037,1057,1059,1077,1081,1133,1137,1145,1149,1159,1169,1227,1243

%N Semiprimes that are not the arithmetic derivative (A003415) of any integer.

%C 17^2 = 289 and 23^2 = 529 are the first squares present.

%o (PARI)

%o A002620(n) = ((n^2)>>2);

%o A003415(n) = if(n<=1, 0, my(f=factor(n)); n*sum(i=1, #f~, f[i, 2]/f[i, 1]));

%o isA351095(n) = if(2!=bigomega(n), 0, for(k=1,A002620(n),if(A003415(k)==n,return(0))); (1));

%Y Complement of A351096 in A001358. Subsequence of A098700 and of A189554.

%Y Cf. A003415, A189483.

%K nonn

%O 1,1

%A _Antti Karttunen_, Feb 03 2022