A141607 Nonprimes of the form n-(p(n+1)-p(n-2))/(p(n)-p(n-1)), where p(n)=n-th prime.

0, 1, 4, 6, 8, 9, 10, 12, 15, 20, 21, 22, 24, 25, 26, 27, 33, 35, 36, 44, 45, 48, 50, 51, 57, 60, 62, 63, 68, 69, 72, 74, 75, 82, 84, 85, 90, 93, 98, 105, 110, 111, 115, 121, 122, 126, 129, 134, 135, 136, 138, 142, 143, 144, 145, 147, 148, 158, 165, 166, 169, 170, 172, 174, 176

Offset

1,3

Comments

Entries are not repeated and shown in natural order.

Links

Table of n, a(n) for n=1..65.

Example

n=4: 4-(11-3)/(7-5)=0=a(1).
n=6: 6-(17-7)/(13-11)=1=a(2).
n=9: 9-(29-17)/(23-19)=6=a(4).
n=10: 10-(31-19)/(29-23)=8=a(5).
n=11: 11-(37-23)/(31-29)=4=a(3).

Mathematica

Select[PrimePi[#[[3]]]-(#[[4]]-#[[1]])/(#[[3]]-#[[2]])&/@ Partition[ Prime[ Range[200]], 4, 1], IntegerQ[#]&&!PrimeQ[#]&]//Union (* Harvey P. Dale, Jul 06 2017 *)

Crossrefs

Cf. A000040.

Sequence in context: A355170 A248010 A067013 * A071070 A275722 A047820

Adjacent sequences: A141604 A141605 A141606 * A141608 A141609 A141610

Keyword

nonn

Author

Juri-Stepan Gerasimov, Sep 10 2008

Extensions

Corrected and extended by R. J. Mathar, Sep 26 2008

Status

approved