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 A141635 Odd nonprimes of the form j/(p(j+1)-p(j)), where p(j)=j-th prime. 1
 1, 1, 1, 9, 9, 49, 91, 95, 35, 115, 117, 69, 143, 147, 159, 87, 25, 95, 195, 69, 215, 75, 57, 243, 249, 129, 265, 267, 135, 279, 35, 153, 39, 105, 161, 323, 329, 69, 117, 363, 387, 105, 423, 429, 217, 435, 437, 147, 225, 153, 93, 243, 245, 249, 125, 515, 87, 525, 527, 177 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,4 COMMENTS The nonprimes are listed in order of increasing j, duplicates retained. LINKS Table of n, a(n) for n=1..60. EXAMPLE If j=1, then 1/(p(1+1)-p(1))=1/(3-2)=1=a(1). If j=2, then 2/(p(2+1)-p(2))=2/(5-3)=1=a(2). If j=4, then 4/(p(4+1)-p(4))=4/(11-7)=1=a(3). If j=54, then 54/(p(54+1)-p(54))=54/(257-251)=9=a(4). If j=72, then 72/(p(72+1)-p(72))=72/(367-359)=9=a(5). If j=98, then 98/(p(98+1)-p(98))=98/(523-521)=49=a(6). MAPLE A141635 := proc() local n, p, p1, q ; n := 1 ; p := ithprime(n); p1 := nextprime(p) ; for n from 1 to 2000 do if n mod (p1-p) = 0 then q := n/(p1-p) ; if not isprime(q) and (q mod 2) = 1 then printf("%d, ", q) ; fi; fi; p := p1 ; p1 := nextprime(p1) ; od: RETURN() ; end: A141635() ; # R. J. Mathar, Sep 13 2008 CROSSREFS Cf. A000040, A141468, A001223. Sequence in context: A188276 A152752 A095344 * A014718 A371374 A339324 Adjacent sequences: A141632 A141633 A141634 * A141636 A141637 A141638 KEYWORD nonn,less AUTHOR Juri-Stepan Gerasimov, Sep 12 2008 EXTENSIONS Corrected from 7th entry on by R. J. Mathar, Sep 13 2008 STATUS approved

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Last modified July 25 15:49 EDT 2024. Contains 374612 sequences. (Running on oeis4.)