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

Author

M. F. Hasler, Jul 30 2016

Keywords

• nonn
• more

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.

Crossrefs

Cf. A006037.

Programs

PARI

print1(s=0);for(k=0,30,print1(","s+=sum(n=1<A006037(2*n))))

Extensions

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

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