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A192495
Smallest prime p such that there is a gap of phi(n) between p and next prime.
1
2, 2, 3, 3, 7, 3, 23, 7, 23, 7, 139, 7, 199, 23, 89, 89, 1831, 23, 523, 89, 199, 139, 1129, 89, 887, 199, 523, 199, 2971, 89, 4297, 1831, 887, 1831, 1669, 199, 9551, 523, 1669, 1831, 19333, 199, 16141, 887, 1669, 1129, 81463, 1831, 16141
OFFSET
1,1
LINKS
FORMULA
a(n) = A000230(phi(n)/2) for n >= 3. - Robert Israel, Jan 10 2017
EXAMPLE
a(9) = 23 because 29 - 23 = 6 = phi(9).
MAPLE
A192495 := proc(n) pn := numtheory[phi](n) ; for i from 1 do if ithprime(i+1) -ithprime(i) = pn then return ithprime(i) ; end if; end do: end proc:
seq(A192495(n), n=1..80) ; # R. J. Mathar, Jul 03 2011
MATHEMATICA
a[n_] := If[n==1, 2, (For[m=1, Prime[m+1]-Prime[m]!= EulerPhi[n], m++ ]; Prime[m])]; Table[a[n], {n, 50}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Lagneau, Jul 02 2011
EXTENSIONS
Corrected by R. J. Mathar, Jul 03 2011
STATUS
approved