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A072999 a(n+1) is the smallest prime>a(n) such that a(n+1) == a(n-1) (mod a(n)). 9
2, 3, 5, 13, 31, 137, 853, 6961, 28697, 179143, 6836131, 68540453, 966402473, 15530980021, 94152282599, 203835545219, 2540178825227, 61168127350667, 6119352913891927, 220357873027460039, 16312601956945934813 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,1
LINKS
EXAMPLE
After 3,5, one can't have composite 8, so keep adding 5 until you reach 13. After 5,13, one can't have composite 18, so keep adding 13 until you reach 31.
MATHEMATICA
nxt[{a_, b_}]:=Module[{c=a+b}, While[CompositeQ[c], c=c+b]; {b, c}]; NestList[ nxt, {2, 3}, 20][[All, 1]] (* Harvey P. Dale, Aug 01 2017 *)
PROG
(PARI) l=2; h=3; print1("2, 3, "); while(l<2^128, t=l+h; while(!isprime(t), t+=h); print1(t, ", "); l=h; h=t)
CROSSREFS
Cf. A083698: partial fraction having these primes as numerators or denominators.
Sequence in context: A041519 A355512 A060434 * A175093 A342180 A345076
KEYWORD
nonn
AUTHOR
Phil Carmody, Aug 15 2002
STATUS
approved

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Last modified June 18 10:02 EDT 2024. Contains 373479 sequences. (Running on oeis4.)