1,1

a(n) = Sum(prime(i)*(2*i-1): 1<=i<=n);

a(n) = 2*A014285(n) - A007504(n).

Eric Weisstein's World of Mathematics, Figurate Number.

............................................ 7

........................... 5 ............ 7 5 7

............ 3 .......... 5 3 5 ........ 7 5 3 5 7

2 ........ 3 2 3 ...... 5 3 2 3 5 .... 7 5 3 2 3 5 7

a(1)=2 ... a(2)=11 .... a(3)=36 ...... a(4)=85.

Cf. A002412.

Sequence in context: A110950 A102744 A145951 this_sequence A022727 A008907 A048246

Adjacent sequences: A083212 A083213 A083214 this_sequence A083216 A083217 A083218

nonn

Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Jun 01 2003