A280895 For any n>=0, least prime k = p^d-2*n, where p is a prime and d is its number of digits.
2, 3, 3, 163, 113, 1030291, 109, 107, 2571337, 103, 101, 2248069, 97, 263, 1442869, 139, 89, 1225009, 2685583, 83, 2571313, 79, 317, 2571307, 73, 71, 1224991, 67, 113, 3307891, 61, 59, 104633567005988371387, 103, 53, 1224973, 97, 47, 1224967, 43, 41, 1030219, 37
Offset: 0
Examples
a(5) = 1030291 because 1030291 is the least prime such that 101^3 - 2*5 = 1030301 - 10 = 1030291.
Links
- Paolo P. Lava, Table of n, a(n) for n = 0..1000
Programs
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Maple
P:=proc(q) local a,b,k,n; for n from 0 to q do for k from 1 to q do a:=ithprime(k); b:=a^(ilog10(a)+1)-2*n; if isprime(b) then lprint(n,b); break; fi; od; od; end: P(1000);