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A048352
a(n)^2 is the smallest square containing exactly n 7's.
2
24, 76, 424, 3576, 8819, 88924, 278874, 2116076, 8819154, 61463576, 277450424, 526087234, 1943470576, 21858013924, 199694210926, 260341642412, 3574601764924, 11156736878576, 27180356468924
OFFSET
1,1
COMMENTS
a(20) > 10^14. - Giovanni Resta, Jul 27 2018
LINKS
Eric Weisstein's World of Mathematics, Square Number
MATHEMATICA
a[n_] := Module[{i = 1}, While[DigitCount[i^2][[7]] != n, i++ ]; i]; (* Sam Handler (sam_5_5_5_0(AT)yahoo.com), Aug 22 2006 *)
CROSSREFS
Sequence in context: A211588 A211596 A214397 * A144459 A290710 A206010
KEYWORD
nonn,base,more
AUTHOR
Patrick De Geest, Mar 15 1999
EXTENSIONS
a(13)-a(16) from Jon E. Schoenfield, Jan 24 2009
a(17)-a(19) from Giovanni Resta, Jul 27 2018
STATUS
approved