A065604 a(n) = smallest k satisfying the equation phi(k) = phi(k-1) + phi(k-2) and having just n prime factors.

3, 1037, 619697, 218688017, 32617225577

Offset: 1

Author

Robert G. Wilson v, Dec 01 2001

Keywords

• hard
• nonn

Examples

			a(1) = 3 which is prime and is the first term in A065557, a(2) = 1037 = 17*61 which is the first term in A065572, a(3) = 619697=13*73*653
		

Crossrefs

Cf. A065557 and A065572.

Programs

Mathematica

a = Table[0, {4}]; x = y = 1; Do[ z = EulerPhi[n]; If[z == x + y, If[l = Length[ FactorInteger[ n]]; a[[l]] == 0, a[[l]] = n; Print[n]]]; x = y; y = z, {n, 3, 10^7 } ]; a

Extensions

a(5) from Donovan Johnson, Feb 05 2010