A135680 a(n) = n if n = 1 or if n is prime. Otherwise, n = 4 if n is even and n = 5 if n is odd.

1, 2, 3, 4, 5, 4, 7, 4, 5, 4, 11, 4, 13, 4, 5, 4, 17, 4, 19, 4, 5, 4, 23, 4, 5, 4, 5, 4, 29, 4, 31, 4, 5, 4, 5, 4, 37, 4, 5, 4, 41, 4, 43, 4, 5, 4, 47, 4, 5, 4, 5, 4, 53, 4, 5, 4, 5, 4, 59, 4, 61, 4, 5, 4, 5, 4, 67, 4, 5, 4, 71, 4, 73

Offset: 1

Author

Mohammad K. Azarian, Dec 01 2007

Keywords

• nonn
• easy

Links

• G. C. Greubel, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A135679.

Programs

Mathematica

Table[Which[n == 1, 1, PrimeQ[n], n, EvenQ[n], 4, True,5], {n, 80}] (* Harvey P. Dale, Jul 22 2012 *)
Table[If[PrimeQ[n] || n == 1, n, If[EvenQ[n], 4, 5]], {n, 25}] (* G. C. Greubel, Oct 26 2016 *)
Join[{1, 2}, Table[Boole[PrimeQ[n]] * (n - 1) + Boole[Not[PrimeQ[n]]] * 4 + Boole[OddQ[n]], {n, 3, 80}]] (* Alonso del Arte, Oct 26 2016 *)