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A117746 Numbers of the form k^2 - k - 1 whose digit sum is also a number of the form k^2 - k - 1. 0
1, 5, 29, 41, 131, 155, 209, 379, 461, 551, 649, 991, 1055, 1121, 1189, 1639, 1721, 1891, 2351, 2449, 2755, 3079, 3305, 3781, 4159, 4421, 4555, 5699, 5851, 6005, 6319, 6805, 7309, 7831, 8371, 9505, 10099, 10301, 10505, 12431, 12655, 13339, 14761 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..43.

EXAMPLE

5699 is in the sequence because 5699 = 76^2 - 76 - 1, the sum of its digits is 5 + 6 + 9 + 9 = 29, and 29 can be written as 6^2 - 6 - 1.

MATHEMATICA

nset=Table[n^2-n-1, {n, 200}]; Rest[Select[nset, MemberQ[nset, Total[ IntegerDigits[ #]]]&]]  (* Harvey P. Dale, Jan 22 2011 *)

CROSSREFS

Sequence in context: A033205 A167742 A107151 * A156053 A081116 A192090

Adjacent sequences:  A117743 A117744 A117745 * A117747 A117748 A117749

KEYWORD

base,nonn

AUTHOR

Luc Stevens (lms022(AT)yahoo.com), Apr 14 2006

STATUS

approved

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Last modified July 19 22:14 EDT 2019. Contains 325168 sequences. (Running on oeis4.)