A038693 - OEIS

A038693

Numbers whose concatenation of prime factors (with multiplicity) is a square.

10, 20, 145, 178, 183, 203, 802, 1131, 1202, 1618, 2436, 2454, 2810, 2867, 3218, 3983, 4645, 4758, 4939, 5602, 6989, 7569, 8166, 8874, 9023, 9298, 9407, 9691, 9821, 10562, 10845, 12205, 13138, 14907, 16739, 16805, 18482, 19443, 19858, 19894, 21445, 26941

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OFFSET

1,1

LINKS

Sean A. Irvine, Table of n, a(n) for n = 1..1000

EXAMPLE

802 = 2*401 and 2401 = 49^2.

1131 = 3*13*29 and 31329 = 177^2.

PROG

(PARI) f(n)={ n<4 & return(n); for(i=1, #n=factor(n)~, n[1, i]=concat(vector(n[2, i], j, Str(n[1, i])))); eval(concat(n[1, ])); } \\ A037276

isok(n) = (n>1) && issquare(f(n)); \\ Michel Marcus, Jan 28 2021

CROSSREFS