A020950 a(n) = k-1, where k is smallest number such that A002487(k) = n.

0, 2, 4, 8, 10, 32, 18, 20, 34, 38, 36, 44, 42, 68, 72, 92, 76, 74, 82, 188, 84, 140, 138, 152, 150, 146, 154, 266, 148, 164, 172, 278, 274, 170, 282, 314, 276, 536, 324, 296, 292, 578, 300, 308, 364, 332, 298, 566, 330, 338, 552, 548, 562, 1274, 340, 584, 564, 614, 628

Offset

1,2

Links

Table of n, a(n) for n=1..59.

Example

A002487(33) = 6 and this is the first time 6 appears, so a(6) = 33-1 = 32.

Prog

(Python)
from itertools import count
from functools import reduce
def A020950(n): return next(filter(lambda k:sum(reduce(lambda x, y:(x[0], x[0]+x[1]) if int(y) else (x[0]+x[1], x[1]), bin(k)[-1:2:-1], (1, 0)))==n, count(1)))-1 # Chai Wah Wu, May 05 2023

Crossrefs

Equals A020946 - 1.

Cf. A020943-A020946, A002487, A020947-A020949.

Sequence in context: A056654 A365002 A370663 * A056386 A331027 A210108

Adjacent sequences: A020947 A020948 A020949 * A020951 A020952 A020953

Keyword

nonn

Author

Clark Kimberling

Extensions

Corrected and extended by David W. Wilson

Status

approved