

A134462


Centered decagonal palindromic primes; or palindromic primes of the form 5n^2 + 5n + 1.


2




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 10gonal 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

Table of n, a(n) for n=1..8.
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 10gonal 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



