OFFSET
1,2
LINKS
Éric Angelini, Sums of distinct prime factors, Personal blog, December 2023.
EXAMPLE
a(1) + a(2) = 1 + 13 = 14 whose sopf is 9, a perfect square.
a(2) + a(3) = 13 + 15 = 28 whose sopf is 9, a perfect square.
a(7) + a(8) = 18 + 21 = 39 whose sopf is 16, a perfect square.
a(8) + a(9) = 21 + 7 = 28 whose sopf is 9, a perfect square.
MATHEMATICA
a[1]=1; a[n_]:=a[n]=(k=1; While[MemberQ[ar=Array[a, n-1], k] ||!IntegerQ@Sqrt@Total[First/@FactorInteger[k+a[n-1]]], k++]; k); Array[a, 70]
CROSSREFS
KEYWORD
nonn
AUTHOR
Giorgos Kalogeropoulos and Eric Angelini, Dec 05 2023
STATUS
approved