A117476 The values of a in a^2 + b^2 = c^2 where b - a = 23 and gcd(a,b,c)=1.
12, 33, 133, 252, 832, 1525, 4905, 8944, 28644, 52185, 167005, 304212, 973432, 1773133, 5673633, 10334632, 33068412, 60234705, 192736885, 351073644, 1123352944, 2046207205, 6547380825, 11926169632, 38160932052, 69510810633
Offset: 1
Examples
a(5) = 6*133 - 12 + 46 = 832 and 832^2 + 855^2 = 1193^2 and 855-832=23 and gcd(832,855,1193)=1
Links
- Index entries for linear recurrences with constant coefficients, signature (1,6,-6,-1,1).
Crossrefs
Cf. A117475.
Formula
a(1)=12, a(2)=33, a(3)=133, a(4)=252, a(n) = 6*a(n-2) - a(n-4) + 46.
G.f.: x*(8*x^4+7*x^3-28*x^2-21*x-12) / ((x-1)*(x^2-2*x-1)*(x^2+2*x-1)). [Colin Barker, Dec 17 2012]
Comments