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A289750 a(1) = 3 and a(n+1) - a(n) = 2*p where p is the least possible prime. 2
3, 7, 11, 17, 23, 29, 43, 47, 53, 59, 73, 79, 83, 89, 103, 107, 113, 127, 131, 137, 151, 157, 163, 167, 173, 179, 193, 197, 211, 233, 239, 277, 281, 307, 311, 317, 331, 337, 347, 353, 359, 373, 379, 383, 389, 463, 467, 541, 547, 557, 563, 569, 607, 613, 617, 631, 641, 647, 653, 659 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Values of p: 2, 2, 3, 3, 3, 7, 2, 3, 3, 7, 3, 2, 3, 7, 2, 3, 7, 2, 3, 7, 3, 3, 2, 3, 3, 7, 2, 7, 11, 3, 19, 2, 13, 2, 3, 7, 3, 5, 3, 3, 7, 3, 2, 3, 37, 2, 37, 3, 5.
For n > 2, a(n) = A255609(n-1). - Jon E. Schoenfield, Nov 26 2017
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
EXAMPLE
a(1000) = 23833 = A000040(2651), a(999) = 23819 = A000040(2649), and a(1000)-a(999) = 14 = 2*A000040(4), while 23819 + {4,6,10} are composite.
PROG
(PARI) step(n)=forprime(p=2, , if(isprime(n+2*p), return(n+2*p)))
first(n)=my(v=vector(n)); v[1]=3; for(n=2, n, v[n]=step(v[n-1])); v \\ Charles R Greathouse IV, Jul 14 2017
CROSSREFS
Sequence in context: A285600 A191050 A081515 * A184856 A023234 A237662
KEYWORD
nonn,easy
AUTHOR
Zak Seidov, Jul 11 2017
STATUS
approved

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Last modified March 28 20:05 EDT 2024. Contains 371254 sequences. (Running on oeis4.)