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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).
0
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
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
KEYWORD
nonn
AUTHOR
Alain Rocchelli, Jan 09 2023
STATUS
approved