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A048391 Replacing digits d in decimal expansion of n with d^3 yields a square. 2
0, 1, 4, 9, 21, 100, 400, 561, 900, 2100, 8821, 10000, 11221, 17821, 40000, 56100, 73221, 90000, 210000, 211201, 518041, 882100, 1000000, 1001614, 1002621, 1012021, 1012224, 1122100, 1302801, 1782100, 4000000, 5012214, 5610000 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..33.

EXAMPLE

E.g. 518041 = (5)(1)(8)(0)(4)(1) -> (125)(1)(512)(0)(64)(1) = 12515120641 = 111871^2 and a square.

MATHEMATICA

Select[Range[0, 561*10^4], IntegerQ[Sqrt[FromDigits[Flatten[ IntegerDigits/@ (IntegerDigits[ #]^3)]]]]&] (* Harvey P. Dale, Apr 15 2019 *)

PROG

(PARI) ccd(n) = {if (n==0, return(0)); my(d = digits(n)); my(nd = ""); for (i=1, #d, nd = Str(nd, d[i]^3); ); eval(nd); }

isok(n) = issquare(ccd(n)); \\ Michel Marcus, Oct 19 2016

CROSSREFS

Cf. A048390, A048392.

Sequence in context: A243640 A243634 A076861 * A041743 A041943 A158140

Adjacent sequences:  A048388 A048389 A048390 * A048392 A048393 A048394

KEYWORD

nonn,base

AUTHOR

Patrick De Geest, Mar 15 1999

EXTENSIONS

Offset corrected by Michel Marcus, Oct 19 2016

STATUS

approved

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Last modified October 15 07:56 EDT 2019. Contains 328026 sequences. (Running on oeis4.)