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A070247 Palindromic primes with digit sum 5. 6
5, 131, 10301, 1003001, 100030001, 100111001, 101000010000101, 10000010101000001, 101000000010000000101, 110000000010000000011, 10000000000300000000001, 10000100000100000100001 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

It is conjectured that are just 3 palindromic primes with digit sum 2, namely 2, 11 and 101. If any others exist, they must be of the form 10^(2^k) +1 with k > 14.

LINKS

Chai Wah Wu, Table of n, a(n) for n = 1..238

Hans Riesel, Some factors of the numbers Gn = 6^2^n+1 and Hn = 10^2^n+1, Math. Comp. 23 (1969), p. 413-415. With errata reported in Math. Comp. 24 (1970), p. 243.

MATHEMATICA

Do[p = Join[ IntegerDigits[n, 4], Reverse[ Drop[ IntegerDigits[n, 4], -1]]]; q = Plus @@ p; If[q == 5 && PrimeQ[ FromDigits[p]] && q == 5, Print[ FromDigits[p]]], {n, 1, 4 10^8}] (* this coding will not pick up the first entry *)

CROSSREFS

Cf. A002385, A070248 & A070249.

Sequence in context: A229879 A145611 A222880 * A171375 A191409 A003372

Adjacent sequences:  A070244 A070245 A070246 * A070248 A070249 A070250

KEYWORD

base,nonn

AUTHOR

Amarnath Murthy, May 05 2002

EXTENSIONS

Edited by Robert G. Wilson v, May 15 2002

STATUS

approved

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Last modified September 27 19:34 EDT 2021. Contains 347694 sequences. (Running on oeis4.)