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

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]

Prog

(Magma) [n : n in [1 .. 2000] | IsPrime (Floor (n^2/10))];
(PARI) isok(n) = isprime(n^2\10); \\ Michel Marcus, Jul 02 2017

Crossrefs

Cf. A024770, A031149, A137812, A227916, A227919, A258032.

Sequence in context: A309480 A180686 A308822 * A145491 A282466 A060724

Adjacent sequences: A289187 A289188 A289189 * A289191 A289192 A289193

Keyword

nonn,base

Author

K. D. Bajpai, Jun 27 2017

Status

approved