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A227090 Numbers n such that n^2+1 with its digits reversed is prime (ignoring leading zeros). 1
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 (list; graph; refs; listen; history; text; internal format)
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: A026144 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

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Last modified May 27 21:12 EDT 2020. Contains 334671 sequences. (Running on oeis4.)