A064961 Composite-then-prime recurrence; a(2n) = a(2n-1)-th composite and a(2n+1) = a(2n)-th prime and a(1) = 1.
1, 4, 7, 14, 43, 62, 293, 366, 2473, 2892, 26317, 29522, 344249, 376259, 5429539, 5831545, 101291779, 107457490, 2198218819, 2310909505, 54720307351, 57128530327, 1543908890351, 1603146693999, 48871886538151, 50527531769529, 1720466016680911, 1772475453490311
Offset: 1
Keywords
Links
- Chai Wah Wu, Table of n, a(n) for n = 1..32
- Andrew R. Booker, The Nth Prime Page
- N. Fernandez, An order of primeness, F(p)
- N. Fernandez, An order of primeness [cached copy, included with permission of the author]
Crossrefs
Programs
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Mathematica
Composite[n_Integer] := FixedPoint[n + PrimePi[ # ] + 1 &, n + PrimePi[n] + 1]; a = {1, 4}; b = 4; Do[ If[ !PrimeQ[b], b = Prime[b], b = Composite[b]]; a = Append[a, b], {n, 1, 23}]; a
Extensions
a(24)-a(26) corrected and a(27)-a(28) added by Chai Wah Wu, Aug 22 2018