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 A030430 Primes of the form 10*n+1. 48
 11, 31, 41, 61, 71, 101, 131, 151, 181, 191, 211, 241, 251, 271, 281, 311, 331, 401, 421, 431, 461, 491, 521, 541, 571, 601, 631, 641, 661, 691, 701, 751, 761, 811, 821, 881, 911, 941, 971, 991, 1021, 1031, 1051, 1061, 1091, 1151, 1171, 1181, 1201, 1231, 1291 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Also primes of form 5*n+1 or equivalently 5*n+6. Primes p such that the arithmetic mean of divisors of p^4 is an integer: A000203(p^4)/A000005(p^4) = C. - Ctibor O. Zizka, Sep 15 2008 Being a subset of A141158, this is also a subset of the primes of form x^2-5*y^2. - Tito Piezas III, Dec 28 2008 Solutions of the equation (10*n+1)'=1, where n' is the arithmetic derivative of n. - Paolo P. Lava, Nov 15 2012 5 is quadratic residue of primes of this form. - Vincenzo Librandi, Jun 25 2014 Primes p such that 5 divides sigma(p^4), cf. A274397. - M. F. Hasler, Jul 10 2016 LINKS Michael B. Porter, Table of n, a(n) for n = 0..100000 A. Granville and G. Martin, Prime number races, arXiv:math/0408319 [math.NT], 2004. FORMULA a(n) = 10*A024912(n+1)+1 = 5*A081759(n)+6. A104146(floor(a(n)/10)) = 1. Union of A132230 and A132232. - Ray Chandler, Apr 07 2009 a(n) ~ 4n log n. - Charles R Greathouse IV, Sep 06 2012 MATHEMATICA Select[Prime@Range[210], Mod[ #, 10] == 1 &] (* Ray Chandler, Dec 06 2006 *) Select[Range[11, 1291, 10], PrimeQ] (*Zak Seidov, Aug 14 2011*) PROG (Haskell) a030430 n = a030430_list !! (n-1) a030430_list = filter ((== 1) . a010051) a017281_list -- Reinhard Zumkeller, Apr 16 2012 (PARI) is(n)==n%10==1 && isprime(n) \\ Charles R Greathouse IV, Sep 06 2012 CROSSREFS Cf. A024912, A045453, A049511, A081759, A017281, A010051, A004615 (multiplicative closure). Cf. A001583 (subsequence). Sequence in context: A038351 A068871 A004615 * A059313 A040975 A188384 Adjacent sequences:  A030427 A030428 A030429 * A030431 A030432 A030433 KEYWORD nonn,easy AUTHOR STATUS approved

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