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 A258436 Primes p of form x^2 - phi(x) such that (p-1)/tau(p-1) is also prime. 0
 157, 1069, 61837, 190573, 840109, 1950349, 2485453, 20616397, 38844349, 57648589, 133091053, 144685357, 188582029, 222029869, 276773389, 346282477, 399067213, 472656589, 827175949, 929558797, 1137622957, 1352220109, 1369037389 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Intersection of A252021 and A258435. LINKS MATHEMATICA lst = Table[n^2 - EulerPhi[n], {n, 100000}]; Select[lst, PrimeQ[#] && PrimeQ[ ( # - 1)/DivisorSigma[0, # - 1] ] &] PROG (PARI) lista(nn) = {for (n=1, nn, if (isprime(p=n^2-eulerphi(n)) && (pp=p-1) && (type(r=pp/numdiv(pp))=="t_INT") && isprime(r), print1(p, ", ")); ); } \\ Michel Marcus, Jul 08 2015 CROSSREFS Cf. A252021, A258435. Sequence in context: A337427 A142766 A326442 * A167992 A038493 A212237 Adjacent sequences:  A258433 A258434 A258435 * A258437 A258438 A258439 KEYWORD nonn,easy AUTHOR Carlos Eduardo Olivieri, May 30 2015 STATUS approved

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Last modified June 12 10:58 EDT 2021. Contains 344947 sequences. (Running on oeis4.)