login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A134463 Values of n such that 5n^2 + 5n + 1 is a palindromic prime. 1
1, 4, 5, 565, 475081, 4565455, 4639740, 4623988479 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Corresponding Centered decagonal palindromic primes are 5a(n)^2 + 5a(n) + 1 = A134462 = {11,101,151,1598951,1128512158211, ...}. Note that the first 4 terms of a(n) are the palindromes.

a(9) > 1414213562372. - 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[ k ] ], {k, 1, 500000} ]

CROSSREFS

Cf. A134462 = Centered decagonal palindromic primes; or palindromic primes of the form 5n^2 + 5n + 1. 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.

Sequence in context: A042181 A042717 A304286 * A298938 A309071 A270975

Adjacent sequences:  A134460 A134461 A134462 * A134464 A134465 A134466

KEYWORD

more,nonn,base

AUTHOR

Alexander Adamchuk, Oct 26 2007

EXTENSIONS

a(6), a(7) from D. S. McNeil, Mar 02 2009

a(8) from Donovan Johnson, Feb 13 2011

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 29 18:37 EDT 2020. Contains 333117 sequences. (Running on oeis4.)