A359650 Smallest prime factor q of (2^(p-1)-1) / (3*p) with prime p such that q is greater than p (increasing p, cf. A359387).

31, 89, 178481, 233, 13367, 6361, 499, 62020897, 3391, 1049, 4153, 1433, 7068569257, 1327, 1399, 1913, 54217, 80929, 26371, 7753, 855857, 5867, 3449, 48731, 7707719, 12619129, 104369, 32051, 78557207, 67219, 1676083, 34513, 22291, 4567, 14563, 830833, 2731, 343081

Offset

1,1

Links

Table of n, a(n) for n=1..38.

Formula

a(n) = A020639(A096060(A000720(A359387(n)))). - Michel Marcus, Jan 14 2023

Example

For p=7,  (2^6-1)/(3*7) = 3 and 3 is not greater than 7.
For p=11, (2^10-1)/(3*11) = 31, which is greater than 11, so a(1)=31.
For p=13, (2^12-1)/(3*13) = 105 = 3*5*7 and 3 is not greater than 13.
For p=17, (2^16-1)/(3*17) = 1285 = 5*257 and 5 is not greater than 17.
For p=19, (2^18-1)/(3*19) = 4599 = 3^2*7*73 and 3 is not greater than 19.
For p=23, (2^22-1)/(3*23) = 60787 = 89*683 and 89 is greater than 23, so a(2)=89.

Crossrefs

Cf. A000720, A020639, A096060, A359387.

Sequence in context: A179113 A142715 A093758 * A360488 A139700 A124803

Adjacent sequences: A359647 A359648 A359649 * A359651 A359652 A359653

Keyword

nonn

Author

Alain Rocchelli, Jan 09 2023

Status

approved