cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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

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%I A038692 #16 Mar 16 2020 09:10:32
%S A038692 25,225,289,361,529,729,2401,2601,2809,4761,5329,5929,7225,7569,11449,
%T A038692 11881,13225,15129,19881,21609,22801,23409,24649,25281,26569,27225,
%U A038692 29241,29929,31329,32761,34969,36481,39601,47961,52441,53361,54289,55225,57121,58081
%N A038692 Square numbers that are concatenations of two or more prime numbers.
%H A038692 Jinyuan Wang, <a href="/A038692/b038692.txt">Table of n, a(n) for n = 1..1000</a>
%F A038692 A038692(n) = A166503(n)^2. As a set, A038692 = A000290 intersection A152242 = A016754 intersection A152242. - _M. F. Hasler_, Mar 19 2012
%t A038692 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 *)
%o A038692 (PARI) forstep(n=1, 300, 2, is_A152242(n^2) & print1(n^2, ", ")) \\ _M. F. Hasler_, Mar 19 2012
%Y A038692 Cf. A166503 (the square roots).
%K A038692 nonn,base
%O A038692 1,1
%A A038692 _Jeff Burch_
%E A038692 Edited by _N. J. A. Sloane_, Oct 18 2009, incorporating corrections from _M. F. Hasler_ and Zak Seidov.