A246649 Integers of the form (2^(k+1) - 1)/(2*k + 1).

1, 1, 17, 1334440654591915542993625911497130241, 948042080603099421350928003060030968743284199473954197137709371401

Offset

1,3

Comments

The next term has 192 digits. - Harvey P. Dale, Feb 05 2019

Links

Table of n, a(n) for n=1..5.

Example

The sum of the numbers row 7 of the triangular array at A027926 is 2^8 - 1 = 255, and the number of numbers in row 7 is 15, and 255/15 = 17; thus 7 is in this sequence, and 17 is in A246649.

Mathematica

z = 140000; u = Select[Range[0, z], IntegerQ[(2^(# + 1) - 1)/(2 # + 1)] &]   (* A246648 *)
v = Table[(2^(u[[k]] + 1) - 1)/(2 u[[k]] + 1), {k, 1, 6}] (* A246649 *)
Select[Table[(2^(n+1)-1)/(2n+1), {n, 0, 250}], IntegerQ] (* Harvey P. Dale, Feb 05 2019 *)

Crossrefs

Cf. A246637, A246648.

Sequence in context: A257305 A128398 A257377 * A210709 A187567 A160145

Adjacent sequences: A246646 A246647 A246648 * A246650 A246651 A246652

Keyword

nonn,easy

Author

Clark Kimberling, Sep 01 2014

Status

approved