A038692 Square numbers that are concatenations of two or more prime numbers.

25, 225, 289, 361, 529, 729, 2401, 2601, 2809, 4761, 5329, 5929, 7225, 7569, 11449, 11881, 13225, 15129, 19881, 21609, 22801, 23409, 24649, 25281, 26569, 27225, 29241, 29929, 31329, 32761, 34969, 36481, 39601, 47961, 52441, 53361, 54289, 55225, 57121, 58081

Offset

1,1

Links

Jinyuan Wang, Table of n, a(n) for n = 1..1000

Formula

A038692(n) = A166503(n)^2. As a set, A038692 = A000290 intersection A152242 = A016754 intersection A152242. - M. F. Hasler, Mar 19 2012

Mathematica

ric[d_] := PrimeQ@ FromDigits@ d || AnyTrue[ TakeDrop[d, #] & /@ Range[ Length[d] - 1], #[[2, 1]] > 0 && PrimeQ@ FromDigits@ #[[1]] && ric@ #[[2]] &]; ok[n_] := If[ EvenQ[n] && Mod[n, 10] != 2, False, ric@ IntegerDigits@ n]; Select[ Range[300]^2, ok] (* Giovanni Resta, Mar 16 2020 *)

Prog

(PARI) forstep(n=1, 300, 2, is_A152242(n^2) & print1(n^2, ", ")) \\ M. F. Hasler, Mar 19 2012

Crossrefs

Cf. A166503 (the square roots).

Sequence in context: A045785 A030484 A225135 * A017330 A135509 A295015

Adjacent sequences: A038689 A038690 A038691 * A038693 A038694 A038695

Keyword

nonn,base

Author

Jeff Burch

Extensions

Edited by N. J. A. Sloane, Oct 18 2009, incorporating corrections from M. F. Hasler and Zak Seidov.

Status

approved