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A152908
Primes p=prime(k) such that p - nonprime(k) is prime and p + nonprime(k) is not prime, where prime(n) is the n-th prime and nonprime(n) is the n-th nonprime starting with nonprime(1) = 0.
1
3, 17, 37, 53, 71, 79, 113, 127, 151, 167, 277, 317, 383, 397, 419, 421, 509, 577, 599, 641, 643, 653, 683, 761, 797, 829, 877, 937, 1049, 1051, 1087, 1097, 1163, 1249, 1283, 1297, 1367, 1439, 1483, 1607, 1699, 1913, 1933, 1993, 2017, 2081, 2089, 2129, 2131
OFFSET
1,1
EXAMPLE
3(2) - 1(2) = 2 (prime) and 3(2) + 1(2) = 4 (nonprime), so 3 is in the sequence.
17(7) - 10(7) = 7 (prime) and 17(7) + 10(7) = 27 (nonprime), so 17 is in the sequence.
37(12) - 18(12) = 19 (prime) and 37(12) + 18(12) = 55 (nonprime), so 37 is in the sequence.
53(16) - 24(16) = 29(prime) and 53(16) + 24(16) = 77 (nonprime), so 53 is in the sequence.
71(20) - 28(20) = 43(prime) and 71(20) + 28(20) = 99 (nonprime), so 71 is in the sequence.
MAPLE
A141468 := proc(n) option remember ; local a; if n = 1 then 0 ; else for a from procname(n-1)+1 do if not isprime(a) then RETURN(a) ; fi; od; fi; end: for n from 1 to 700 do p := ithprime(n) ; if isprime( p- A141468(n)) and not isprime(p+A141468(n)) then printf("%d, ", p) ; fi; od: # R. J. Mathar, Jan 17 2009
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
227, 619, 1039, etc. removed, and 797, 1087, etc. added, by R. J. Mathar, Jan 17 2009
Better definition from Michel Marcus, Aug 07 2017
STATUS
approved