A227090 Numbers n such that n^2+1 with its digits reversed is prime (ignoring leading zeros).

1, 2, 4, 6, 7, 10, 12, 13, 18, 19, 27, 28, 30, 31, 35, 38, 39, 40, 41, 55, 57, 59, 60, 61, 62, 84, 86, 87, 88, 89, 96, 97, 99, 101, 103, 105, 108, 112, 116, 117, 119, 124, 131, 136, 138, 139, 140, 175, 177, 178, 179, 181, 183, 184, 190, 191, 193, 194, 196, 199, 265, 266, 268, 272, 273, 276, 277, 279, 280, 281, 300, 304, 305

Offset

1,2

Links

K. D. Bajpai, Table of n, a(n) for n = 1..1200

Example

a(3)=4: 4^2+1=17.  Reversing the digits gives 71 which is prime.

Maple

with(StringTools):K:= proc()local i, a, b, c; c:=1; for i from 1 to 10000 do; a:=parse(Reverse(convert((i^2+1), string))); b:=isprime(a); if b then lprint(c, i); c:=c+1; fi; od; end:K(); # K. D. Bajpai, Jun 30 2013
with(StringTools):K := proc(n) local i, a; a:=parse(Reverse(convert((n^2+1), string))):
if (isprime(a)) then RETURN (n) fi: end: seq(K(n), n=1..1500); # K. D. Bajpai, Jun 30 2013

Crossrefs

Cf. A002522, A004086.

Sequence in context: A353072 A286047 A325426 * A047510 A189030 A198033

Adjacent sequences: A227087 A227088 A227089 * A227091 A227092 A227093

Keyword

nonn,base

Author

K. D. Bajpai, Jun 30 2013

Status

approved