A275487 Number of weird numbers (A006037) less than 2^n.

0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 2, 2, 3, 6, 25, 66, 134, 266, 505, 952, 1850, 3515, 6643, 12920, 26893, 55786, 114992, 234719, 473299, 946406, 1884728, 3754316, 7467998, 14845968, 29628007, 59231668, 118528637

Offset

0,11

Comments

It is known that the density of weird numbers is positive, but smaller than 0.0101. The three smallest weird numbers are 70, 836 and 4030, therefore a(n) = 0 for n < 7; a(n) = 1 for 7 <= n < 10, and a(n) = 2 for 10 <= n < 12.

Links

Table of n, a(n) for n=0..36.

Prog

(PARI) print1(s=0); for(k=0, 30, print1(", "s+=sum(n=1<<k, 2<<k, is_A006037(2*n))))

Crossrefs

Cf. A006037.

Sequence in context: A192366 A318039 A060631 * A096100 A260161 A195694

Adjacent sequences: A275484 A275485 A275486 * A275488 A275489 A275490

Keyword

nonn,more

Author

M. F. Hasler, Jul 30 2016

Extensions

a(25)-a(33) from Amiram Eldar, Mar 17 2019

a(34)-a(36) from Amiram Eldar, May 26 2023

Status

approved