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%I #8 Nov 06 2015 02:02:24
%S 5,131,10301,1003001,100030001,100111001,101000010000101,
%T 10000010101000001,101000000010000000101,110000000010000000011,
%U 10000000000300000000001,10000100000100000100001
%N Palindromic primes with digit sum 5.
%C 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.
%H Chai Wah Wu, <a href="/A070247/b070247.txt">Table of n, a(n) for n = 1..238</a>
%H Hans Riesel, <a href="http://www.ams.org/journals/mcom/1969-23-106/S0025-5718-1969-0245507-6/">Some factors of the numbers Gn = 6^2^n+1 and Hn = 10^2^n+1,</a> Math. Comp. 23 (1969), p. 413-415. With errata reported in Math. Comp. 24 (1970), p. 243.
%t 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 *)
%Y Cf. A002385, A070248 & A070249.
%K base,nonn
%O 1,1
%A _Amarnath Murthy_, May 05 2002
%E Edited by _Robert G. Wilson v_, May 15 2002
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