18339

Appears in sequences

• a(n) = p(1)p(n) + p(2)p(n-1) + ... + p(k)p(n+1-k), where k = [ (n+1)/2 ], p = A000040 = the primes.at n=27A024697
• a(n) = p(1)p(n) + p(2)p(n-1) + ... + p(k)p(n-k+1), where k = [ n/2 ], p = A000040, the primes.at n=27A025129
• Minimal positive solution a(n) of Diophantine equation a(n)^2 - a(n)*b(n) - G(n)*b(n)^2 = +1 or -1 with G(n) := A078358(n). The companion sequence is b(n)=A077058(n).at n=26A077057
• a(1)=1. a(n) = a(n-1) + sum of the triangular numbers which are among the first (n-1) terms of the sequence.at n=34A100963