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A038693 Numbers whose concatenation of prime factors (with multiplicity) is a square. 1
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 (list; graph; refs; listen; history; text; internal format)
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

Cf. A037276.

Sequence in context: A006993 A327971 A250107 * A217318 A239237 A018990

Adjacent sequences:  A038690 A038691 A038692 * A038694 A038695 A038696

KEYWORD

nonn,base

AUTHOR

Jeff Burch

EXTENSIONS

Missing terms inserted and terms sorted by Sean A. Irvine, Jan 27 2021

STATUS

approved

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Last modified September 18 00:40 EDT 2021. Contains 347493 sequences. (Running on oeis4.)