a(0) = 1; thereafter, a(n) is the smallest number such that Sum_{m = 0 .. n-1} a(m)*a(m+1) is a square.

nonn,new

nonn

a(n) is the smallest number such that Sum_{m = 0 .. n-1} a(m)*a(m+1) is a square.

1, 1, 3, 4, 5, 9, 7, 16, 9, 25, 11, 36, 13, 49, 15, 23, 120, 14, 52, 88, 33, 80, 21, 112, 102, 152, 30, 224, 165, 136, 105, 7, 636, 309, 304, 252, 103, 1275, 217, 117, 391, 2004, 489, 637, 195, 556, 1736, 500, 91, 1971, 440, 251, 4809, 1216, 291, 3796, 53, 3969

0,3

a(4) = 5 because a(0)*a(1)+a(1)*a(2)+a(2)*a(3)+a(3)*a(4) = 1*1+1*3+3*4+4*5 = 36

nonn

Jonathan Ayres (jonathan.ayres(AT)btinternet.com), Oct 29 2001

approved