A275487 - OEIS

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

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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