A351095 Semiprimes that are not the arithmetic derivative (A003415) of any integer.

35, 57, 65, 93, 145, 177, 205, 209, 217, 219, 237, 289, 303, 305, 323, 377, 393, 413, 415, 427, 453, 473, 485, 497, 515, 517, 529, 533, 537, 553, 597, 629, 681, 697, 699, 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

Offset

1,1

Comments

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

Links

Table of n, a(n) for n=1..62.

Prog

(PARI)
A002620(n) = ((n^2)>>2);
A003415(n) = if(n<=1, 0, my(f=factor(n)); n*sum(i=1, #f~, f[i, 2]/f[i, 1]));
isA351095(n) = if(2!=bigomega(n), 0, for(k=1, A002620(n), if(A003415(k)==n, return(0))); (1));

Crossrefs

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

Cf. A003415, A189483.

Sequence in context: A242291 A078819 A189554 * A267738 A219806 A095958

Adjacent sequences: A351092 A351093 A351094 * A351096 A351097 A351098

Keyword

nonn

Author

Antti Karttunen, Feb 03 2022

Status

approved