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A028839 Sum of digits of n is a square. 17
1, 4, 9, 10, 13, 18, 22, 27, 31, 36, 40, 45, 54, 63, 72, 79, 81, 88, 90, 97, 100, 103, 108, 112, 117, 121, 126, 130, 135, 144, 153, 162, 169, 171, 178, 180, 187, 196, 202, 207, 211, 216, 220, 225, 234, 243, 252, 259, 261, 268, 270, 277, 286, 295, 301, 306, 310 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Difference between two consecutive terms is never equal to 8. - Carmine Suriano, Mar 31 2014

In this sequence, there is no number of the form 3*k-1. In other words, if a(n) is not divisible by 9, it must be of the form 3*k+1. - Altug Alkan, Apr 08 2016

LINKS

Carmine Suriano, Table of n, a(n) for n = 1..1242

EXAMPLE

234511 belongs to the sequence as its sum of digits is 16, a square.

MATHEMATICA

Select[ Range[ 500 ], IntegerQ[ Sqrt[ Apply[ Plus, IntegerDigits[ # ] ] ] ]& ]

PROG

(MAGMA) [n: n in [1..400] | IsSquare(&+Intseq(n))];  // Bruno Berselli, May 26 2011

(PARI) isok(n) = issquare(sumdigits(n)); \\ Michel Marcus, Oct 30 2014

CROSSREFS

Cf. A007953, A028837, A050626.

Cf. A053057 (squares whose digit sum is also a square).

Sequence in context: A020672 A028837 A178241 * A141833 A140292 A208980

Adjacent sequences:  A028836 A028837 A028838 * A028840 A028841 A028842

KEYWORD

nonn,base,easy

AUTHOR

N. J. A. Sloane.

EXTENSIONS

More terms from Erich Friedman

STATUS

approved

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Last modified April 25 00:32 EDT 2017. Contains 285346 sequences.