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 A134462 Centered decagonal palindromic primes; or palindromic primes of the form 5n^2 + 5n + 1. 2
 11, 101, 151, 1598951, 1128512158211, 104216919612401, 107635959536701, 106906347292743609601 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS a(n) is an intersection of the Palindromic primes = A002385(n) = {2, 3, 5, 7, 11, 101, 131, 151, ...} and the Centered 10-gonal numbers = A062786(n) = {1, 11, 31, 61, 101, 151, ...}. Corresponding numbers n such that 5n^2 + 5n + 1 is a term of A134462 are listed in A134463 = {1, 4, 5, 565, 475081, ...}. Note that the first 4 terms of A134463 are the palindromes. a(9) > 10^25. - Donovan Johnson, Feb 13 2011 LINKS Eric Weisstein's World of Mathematics, Palindromic Prime Wikipedia, Centered decagonal number. MATHEMATICA Do[ f=5k^2+5k+1; If[ PrimeQ[f] && FromDigits[ Reverse[ IntegerDigits[ f ] ] ] == f, Print[ f ] ], {k, 1, 500000} ] CROSSREFS Cf. A002385 = Palindromic primes. Cf. A062786 = Centered 10-gonal numbers. Cf. A090562 = Primes of the form 5k^2 + 5k + 1. Cf. A090563 = Values of n such that 5n^2 + 5n + 1 is a prime. Cf. A134463 = Values of n such that 5n^2 + 5n + 1 is a palindromic prime. Sequence in context: A052035 A083144 A058411 * A156753 A118592 A156617 Adjacent sequences:  A134459 A134460 A134461 * A134463 A134464 A134465 KEYWORD more,nonn,base AUTHOR Alexander Adamchuk, Oct 26 2007 EXTENSIONS More terms from Tomas J. Bulka (tbulka(AT)rodincoil.com), Aug 30 2009 a(8) from Donovan Johnson, Feb 13 2011 STATUS approved

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Last modified April 8 03:01 EDT 2020. Contains 333312 sequences. (Running on oeis4.)