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Sum of digits of pentagonal numbers.
0

%I #8 Dec 26 2021 20:51:45

%S 1,5,3,4,8,6,7,11,9,10,14,3,13,17,6,16,11,18,10,14,12,13,17,15,16,2,9,

%T 10,14,12,13,8,15,16,11,18,10,14,12,13,8,15,16,20,9,10,14,12,22,17,24,

%U 7,20,18,10,23,21,13,17,15,16,20,18,10,14,12,13,17,15,16,20,18,28,23,12,22,26

%N Sum of digits of pentagonal numbers.

%t Table[Total[IntegerDigits[(n(3n-1))/2]],{n,80}] (* _Harvey P. Dale_, Jan 20 2015 *)

%Y Cf. A000326.

%K nonn,base

%O 1,2

%A _N. J. A. Sloane_