A023858 a(n) = 1*t(n) + 2*t(n-1) + ... + k*t(n+1-k), where k = floor((n+1)/2), t = A023531.

0, 1, 2, 0, 1, 2, 3, 4, 6, 2, 3, 4, 5, 7, 9, 11, 13, 5, 6, 8, 10, 12, 14, 16, 18, 20, 23, 11, 13, 15, 17, 19, 21, 23, 26, 29, 32, 35, 38, 20, 22, 24, 26, 29, 32, 35, 38, 41, 44, 47, 50, 53, 56, 32, 35, 38, 41, 44, 47, 50, 53, 56, 59, 62, 66, 70, 74, 78, 82, 50, 53, 56, 59, 62, 65, 68, 72, 76, 80, 84, 88, 92

Offset: 1

Author

Clark Kimberling

Keywords

• nonn

Programs

Mathematica

Array[Sum[k Boole@ IntegerQ@ Sqrt[8 # + 9] &[# + 1 - k], {k, Floor[(# + 1)/2]}] &, 82] (* Michael De Vlieger, Jun 12 2019 *)

Formula

a(n) = Sum_{k=1..floor((n+1)/2)} A023531(n+1-k). - Sean A. Irvine, Jun 11 2019

Extensions

Missing a(21)=10 inserted and title simplified by Sean A. Irvine, Jun 11 2019