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 A258435 Primes of form x^2 - phi(x) in increasing order. 4
 3, 7, 43, 157, 1069, 1201, 4177, 4423, 5869, 6163, 8209, 17581, 19183, 22651, 26407, 37057, 48649, 60793, 61837, 82129, 89137, 102829, 113233, 115981, 121453, 141793, 143263, 190573, 208393, 230929, 283609, 292141, 303097, 314401, 337069 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Amiram Eldar, Table of n, a(n) for n = 1..10000 EXAMPLE a(1) = 3, because 2^2 - 1 = 3, and 1^2 - 1 = 0 is not a prime. a(2) = 7, since 3^2 = 9, phi(3) = 2, so 9-2 = 7 (prime). a(3) = 43, since 7^2 = 49, phi(7) = 6, so 49-6 = 43 (prime). a(6) = 1201, since 35^2 = 1225, phi(35) = 24, so 1225-24 = 1201 (prime). MATHEMATICA lst = Table[n^2 - EulerPhi[n], {n, 1000}]; Select[lst, PrimeQ] Select[Table[n^2 - EulerPhi[n], {n, 1000}], PrimeQ] (* Vincenzo Librandi, Jun 03 2015 *) PROG (Magma) [a: n in [1..1000] | IsPrime(a) where a is n^2-EulerPhi(n) ]; // Vincenzo Librandi, Jun 03 2015 (PARI) lista(nn) = {for (n=1, nn, if (isprime(p=n^2 -eulerphi(n)), print1(p, ", ")); ); } \\ Michel Marcus, Jul 08 2015 CROSSREFS Subset of A258434. For phi see A000010. A074268 is a subsequence. - Michel Marcus, Jun 19 2015 Cf. A259145. Sequence in context: A050633 A107636 A303160 * A074268 A019026 A181729 Adjacent sequences: A258432 A258433 A258434 * A258436 A258437 A258438 KEYWORD nonn,easy AUTHOR Carlos Eduardo Olivieri, May 30 2015 EXTENSIONS More terms from Vincenzo Librandi, Jun 03 2015 Edited by Wolfdieter Lang, Jun 16 2015 STATUS approved

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Last modified July 12 17:45 EDT 2024. Contains 374251 sequences. (Running on oeis4.)