A229701 - OEIS

%I #17 Oct 04 2013 11:19:05

%S 1,9,63,1,522,144,487,6921,5202,5203,6534,4806,1828,52011,441,69481,

%T 90432,14292,163,144,16335,90046,67167,9,526501,102321,488241,638461,

%U 522981,522612,610642,487872,127413,520453,9693,655344,902494,180945,4806,4276,123147

%N Squares of triangular numbers, written backwards.

%H K. D. Bajpai, <a href="/A229701/b229701.txt">Table of n, a(n) for n = 1..1000</a>

%F n-th triangular number = T(n) = n*(n+1)/2.

%e a(3) = 63: T(3) = 3/2*(3+1) = 6 and 6^2 = 36. Writing it backwards gives 63.

%e a(6) = 144: T(6) = 6/2*(6+1) = 21 and 21^2 = 441. Writing it backwards gives 144.

%p with(StringTools):KD:= proc() local a; a:= parse(Reverse(convert(((n/2*(n+1))^2),string))); RETURN (a): end: seq(KD(),n=1..100);

%t Table[FromDigits[Reverse[IntegerDigits[(n*(n + 1)/2)^2]]], {n, 1, 100}]

%Y Cf. A004158.

%K nonn,base,less

%O 1,2

%A _K. D. Bajpai_, Sep 27 2013