A268519 Odd powers of 2 written between a pair of 1's.

121, 181, 1321, 11281, 15121, 120481, 181921, 1327681, 11310721, 15242881, 120971521, 183886081, 1335544321, 11342177281, 15368709121, 121474836481, 185899345921, 1343597383681, 11374389534721, 15497558138881, 121990232555521, 187960930222081, 1351843720888321, 11407374883553281

Offset

1,1

Links

Table of n, a(n) for n=1..24.

Marius Coman, Sequences of Integers, Conjectures and New Arithmetical Tools, Education Publishing, Columbus, Ohio, 2015. See page 24.

Mathematica

a[n_]:=10^(Floor[Log10[2^(2n-1)]]+2)+10*2^(2n-1)+1; Array[a, 24] (* Stefano Spezia, Sep 26 2025 *)

Crossrefs

Cf. A000079, A004171.

For primes see A268520.

Sequence in context: A284643 A074730 A393215 * A364778 A037050 A275028

Adjacent sequences: A268516 A268517 A268518 * A268520 A268521 A268522

Keyword

nonn,base

Author

N. J. A. Sloane, Feb 10 2016

Status

approved