A350537 Smallest number m > 1 such that (2n+1)*m = A350536(n) contains only odd digits.

3, 3, 3, 5, 11, 3, 3, 5, 3, 3, 15, 5, 3, 5, 11, 3, 3, 5, 3, 3, 13, 13, 3, 11, 11, 3, 3, 13, 3, 3, 13, 5, 3, 5, 11, 5, 7, 5, 7, 5, 17, 11, 7, 11, 11, 21, 15, 21, 35, 101, 11, 5, 3, 5, 11, 3, 3, 5, 3, 3, 11, 11, 3, 11, 15, 3, 3, 13, 7, 7, 11, 5, 11, 5, 13, 5, 9, 5, 47, 5

Offset

0,1

Comments

Record values of a(n) are 3, 5, 11, 15, 17, 21, 35, 101, 155, ...

Links

Michael De Vlieger, Table of n, a(n) for n = 0..10000

Formula

a(n) = A350536(n) / (2n+1).

Example

The smallest proper multiple of 21 = 2*10+1 with only odd digits is A350536(10) = 315, as 315 = 21 * 15, a(10) = 15.

Mathematica

Table[m=2; While[Or@@EvenQ[IntegerDigits[(2n+1)*++m]]]; m, {n, 0, 79}] (* Giorgos Kalogeropoulos, Jan 12 2022 *)

Prog

(PARI) isok(k) = my(d=digits(k)); #d == #select(x->((x%2)==1), d);
a(n) = my(k=6*n+3); while (!isok(k), k+=4*n+2); k/(2*n+1); \\ Michel Marcus, Jan 12 2022

Crossrefs

Cf. A078221, A296009, A350536, A350538, A350697.

Sequence in context: A358452 A261450 A100026 * A367555 A100049 A261926

Adjacent sequences: A350534 A350535 A350536 * A350538 A350539 A350540

Keyword

nonn,base

Author

Bernard Schott, Jan 12 2022

Extensions

More terms from Michel Marcus, Jan 12 2022

Status

approved