A372584 a(n) = number of odd digits in odd positions in the decimal expansion of n, where position 1 is the least significant digit.

0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2

Offset

0,102

Comments

Corresponds to function a(n) in Borwein and Borwein (1992), p. 622.

First differs from A000035 at n = 100.

Links

Paolo Xausa, Table of n, a(n) for n = 0..10000

J. M. Borwein and P. B. Borwein, Strange Series and High Precision Fraud, The American Mathematical Monthly, Vol. 99, No. 7 (1992), pp. 622-640.

Formula

Sum_{k >= 0} a(k)/10^k is approximately 10/99 (correct to 99 digits).

Mathematica

Array[Count[Reverse[IntegerDigits[#]][[1;; -1;; 2]], _?OddQ] &, 120, 0]

Crossrefs

Cf. A000035.

Sequence in context: A022927 A063435 A262352 * A167964 A280193 A327767

Adjacent sequences: A372581 A372582 A372583 * A372585 A372586 A372587

Keyword

nonn,base,easy

Author

Paolo Xausa, May 06 2024

Extensions

More than the usual number of terms are shown in order to distinguish this from A000035.

Status

approved