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

Author

Clark Kimberling

Keywords

• nonn

Examples

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

Crossrefs

Equals A020946 - 1.

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

Programs

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

Extensions

Corrected and extended by David W. Wilson