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%I #24 Jun 11 2021 18:53:23
%S 1,4,5,565,475081,4565455,4639740,4623988479,5760242508141202328
%N Values of k such that 5k^2 + 5k + 1 is a palindromic prime.
%C Corresponding centered decagonal palindromic primes are 5k^2 + 5k + 1 = A134462 = {11, 101, 151, 1598951, 1128512158211, ...}. Note that the first 4 terms of A134463 are palindromic as well.
%C a(9) > 1414213562372. - _Donovan Johnson_, Feb 13 2011
%C a(10) > 14142135623730950488. - _Patrick De Geest_, May 29 2021
%H Patrick De Geest, <a href="http://www.worldofnumbers.com/centered.htm">Palindromic Centered Polygonal Numbers</a>
%H Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PalindromicPrime.html">Palindromic Prime</a>
%H Wikipedia, <a href="https://en.wikipedia.org/wiki/Centered_decagonal_number">Centered decagonal number</a>
%t Do[ f=5k^2+5k+1; If[ PrimeQ[f] && FromDigits[ Reverse[ IntegerDigits[ f ] ] ] == f, Print[ k ] ], {k, 1, 500000} ]
%Y Cf. A134462 = Centered decagonal palindromic primes; or palindromic primes of the form 5k^2 + 5k + 1.
%Y Cf. A002385 = Palindromic primes.
%Y Cf. A062786 = Centered 10-gonal numbers.
%Y Cf. A090562 = Primes of the form 5k^2 + 5k + 1.
%Y Cf. A090563 = Values of k such that 5k^2 + 5k + 1 is a prime.
%K more,nonn,base
%O 1,2
%A _Alexander Adamchuk_, Oct 26 2007
%E a(6), a(7) from _D. S. McNeil_, Mar 02 2009
%E a(8) from _Donovan Johnson_, Feb 13 2011
%E a(9) from _Patrick De Geest_, May 29 2021
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