A289190 - OEIS

A289190

Numbers k such that k^2 with last digit deleted is a prime.

5, 6, 14, 26, 44, 46, 56, 64, 74, 76, 86, 94, 106, 146, 154, 164, 206, 226, 236, 244, 254, 256, 274, 286, 296, 304, 314, 326, 344, 346, 364, 424, 436, 446, 454, 464, 506, 524, 536, 596, 614, 664, 674, 676, 686, 694, 706, 764, 776, 796, 826, 844, 854, 874, 944, 946

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Marius A. Burtea, Table of n, a(n) for n = 1..545

EXAMPLE

14 is in the sequence because 14^2 = 196; deleting the last digit gives 19 which is prime.

26 is in the sequence because 26^2 = 676; deleting the last digit gives 67 which is prime.

MAPLE

select(n -> isprime(floor(n^2/10)), [$1..2000]);

MATHEMATICA

fQ[n_] := PrimeQ@Quotient[n^2, 10]; Select[Range[1, 2000], fQ]