A120490 1 + Sum[ k^(n-1), {k,1,n}].

2, 4, 15, 101, 980, 12202, 184821, 3297457, 67731334, 1574304986, 40851766527, 1170684360925, 36720042483592, 1251308658130546, 46034015337733481, 1818399978159990977, 76762718946972480010, 3448810852242967123282

Offset: 1

Author

Alexander Adamchuk, Aug 04 2006

Keywords

• nonn

Comments

Prime p divides a(p). Prime p divides a(p-2) for p>3. p^2 divides a(p-2) for prime p=7. p^2 divides a(p^2-2) for prime p except p=3. p^3 divides a(p^2-2) for prime p=7. p^3 divides a(p^3-2) for prime p>3. p^4 divides a(p^3-2) for prime p=7. p^4 divides a(p^4-2) for prime p>3. p^5 divides a(p^3-2) for prime p=7. It appears that p^k divides a(p^k-2) for prime p>3 and 7^(k+1) divides a(7^k-2) for integer k>0.

Crossrefs

Cf. A076015.

Programs

Mathematica

Table[(1+Sum[k^(n-1),{k,1,n}]),{n,1,23}]

Formula

a(n) = 1 + Sum[ k^(n-1), {k,1,n}]. a(n) = 1 + A076015[n].