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A232655 Primes p such that reversal (p^2+p) is also prime. 1
5, 13, 19, 103, 139, 181, 193, 271, 277, 313, 379, 433, 577, 619, 631, 853, 859, 883, 1093, 1117, 1123, 1237, 1279, 1321, 1741, 1873, 1933, 1987, 2659, 2707, 2713, 2719, 2767, 2791, 3163, 3217, 3271, 3331, 3469, 3529, 3547, 3631, 3637, 3727, 3907, 3943, 4129, 4177 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

K. D. Bajpai, Table of n, a(n) for n = 1..6650

EXAMPLE

a(2)= 13, it is prime: n= 6, prime(6)= 13: reversal(13^2+13)= 281, which is also prime.

a(4)= 103, it is prime: n= 27, prime(27)= 103: reversal(103^2+103)= 21701, which is also prime.

a(6)= 181, it is prime: n= 42, prime(42)= 181: reversal(181^2+181)= 24923, which is also prime.

MAPLE

with(StringTools): KD:= proc() local a, p; p:=ithprime(n); a:= parse(Reverse(convert((p^2+p), string))); if isprime(a) then RETURN (p): fi; end: seq(KD(), n=1..3000);

MATHEMATICA

Select[Prime[Range[3000]], PrimeQ[FromDigits[Reverse[IntegerDigits[#^2 + #]]]] &]

CROSSREFS

Cf. A004087 (primes written backwards).

Cf. A061783 (primes p: p+(p reversed)is also prime).

Cf. A232446 (primes p: reversal(p^2)+p is also prime).

Sequence in context: A045455 A160031 A154634 * A175866 A227500 A265814

Adjacent sequences:  A232652 A232653 A232654 * A232656 A232657 A232658

KEYWORD

nonn,base,less

AUTHOR

K. D. Bajpai, Nov 27 2013

STATUS

approved

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Last modified September 19 23:31 EDT 2019. Contains 327207 sequences. (Running on oeis4.)