A119991 - OEIS

A119991

a(n) = n-th positive integer which is coprime to the n-th composite positive integer.

1, 5, 5, 5, 11, 17, 15, 14, 17, 29, 27, 20, 27, 41, 18, 33, 25, 41, 71, 39, 34, 45, 33, 71, 51, 41, 67, 97, 63, 56, 63, 95, 38, 83, 55, 77, 109, 52, 89, 62, 83, 157, 87, 76, 89, 62, 155, 101, 76, 143, 151, 105, 98, 113, 71, 181, 141, 86, 119, 209, 81, 125, 97, 139, 241, 83

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OFFSET

1,2

LINKS

Table of n, a(n) for n=1..66.

EXAMPLE

1,2,4,5,7,8,10,11,...is the sequence of positive integers which are coprime to the 4th composite = 9. 5 is the 4th such integer, so a(4) = 5.

MAPLE

A119991 := proc(nmax) local a, n, i, j, ncomp ; ncomp := [] ; n := 4 ; while nops(ncomp) < nmax do if not isprime(n) then ncomp := [op(ncomp), n] ; fi ; n := n+1 ; od ; a := [] ; for n from 1 to nops(ncomp) do j := 0 ; i := 1 ; while true do if gcd(i, ncomp[n]) = 1 then j := j+1 ; if j = n then a := [op(a), i] ; break ; fi ; fi ; i := i+1 ; od ; od ; RETURN(a) ; end: an := A119991(100) : for i from 1 to nops(an) do printf("%d, ", an[i]) ; od ; # R. J. Mathar, Aug 06 2006

CROSSREFS

Sequence in context: A127310 A214925 A101597 * A262947 A265821 A266953

Adjacent sequences: A119988 A119989 A119990 * A119992 A119993 A119994

KEYWORD

nonn

AUTHOR

Leroy Quet, Aug 03 2006

EXTENSIONS

More terms from R. J. Mathar, Aug 06 2006

STATUS

approved