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 A124106 Octagonal numbers equal to S*(3S - 2) with 3S - 2 = k^2 and S semiprime. 1

%I

%S 96,225,1408,3400,9633,22016,43681,53600,93633,130625,152776,205408,

%T 308481,446216,696008,1493896,1628033,3280256,4617761,4928008,5595136,

%U 6720033,8473921,11721633,19995008,20919361,22863841,30752008,33340000

%N Octagonal numbers equal to S*(3S - 2) with 3S - 2 = k^2 and S semiprime.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/OctagonalNumber.html">Octagonal Number.</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Semiprime.html">Semiprime.</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/16-Cell.html">16-Cell</a>

%F a(n) = A112392(n)*A112393(n).

%Y Cf. A112392, A112393.

%K easy,nonn

%O 1,1

%A _Giovanni Teofilatto_, Dec 13 2006, Dec 14 2006

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Last modified December 6 19:22 EST 2019. Contains 329809 sequences. (Running on oeis4.)