cp's OEIS Frontend

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).

%I A359650 #11 Jan 21 2023 02:42:41
%S A359650 31,89,178481,233,13367,6361,499,62020897,3391,1049,4153,1433,
%T A359650 7068569257,1327,1399,1913,54217,80929,26371,7753,855857,5867,3449,
%U A359650 48731,7707719,12619129,104369,32051,78557207,67219,1676083,34513,22291,4567,14563,830833,2731,343081
%N 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).
%F A359650 a(n) = A020639(A096060(A000720(A359387(n)))). - _Michel Marcus_, Jan 14 2023
%e A359650 For p=7,  (2^6-1)/(3*7) = 3 and 3 is not greater than 7.
%e A359650 For p=11, (2^10-1)/(3*11) = 31, which is greater than 11, so a(1)=31.
%e A359650 For p=13, (2^12-1)/(3*13) = 105 = 3*5*7 and 3 is not greater than 13.
%e A359650 For p=17, (2^16-1)/(3*17) = 1285 = 5*257 and 5 is not greater than 17.
%e A359650 For p=19, (2^18-1)/(3*19) = 4599 = 3^2*7*73 and 3 is not greater than 19.
%e A359650 For p=23, (2^22-1)/(3*23) = 60787 = 89*683 and 89 is greater than 23, so a(2)=89.
%Y A359650 Cf. A000720, A020639, A096060, A359387.
%K A359650 nonn
%O A359650 1,1
%A A359650 _Alain Rocchelli_, Jan 09 2023