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%I #8 Mar 31 2012 10:24:16
%S 8,23,46,59,108,106,156,182,346,348,542,766,727,717,1071,1153,977,
%T 1640,1739,1703,2019,1841,1834,2628,2668,2804,2278,2679,2817,2918,
%U 4105,4243,4921,4028,5936,5528,4728,7302,8576,7453,7184,9516,9630,11107,11828,11889,12241
%N Side of triangle of the sum of pairs of triangular numbers whose sum and difference are triangular.
%D Albert H. Beiler, Recreations in the theory of numbers, New York, Dover, (2nd ed.) 1966, p. 197, nr. 8.
%e a(2) = 23, since the pair of triangular numbers 171 = 18*(18+1)/2 and 105 = 14*(14+1)/2 produce the sum 276 = 23*(23+1)/2 and the difference 66 = 11*(11+1)/2 which are both triangular numbers.
%Y Cf. A000217, A185128, A185129, A185223, A185233, A185243, A185253, A185258.
%K nonn
%O 1,1
%A _Martin Renner_, Jan 20 2012