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A099910
Number of distinct prime-factors of ((prime(n)*(prime(n+1)-1)+(prime(n)-1)*prime(n+1))/2).
2
1, 1, 2, 1, 2, 2, 2, 1, 2, 3, 2, 1, 3, 1, 2, 1, 2, 2, 2, 3, 2, 2, 4, 3, 1, 2, 2, 3, 3, 2, 2, 3, 2, 1, 2, 3, 3, 3, 2, 3, 3, 1, 2, 3, 3, 3, 3, 3, 3, 2, 2, 2, 3, 2, 1, 2, 3, 4, 1, 2, 2, 2, 2, 3, 2, 2, 2, 2, 3, 2, 4, 4, 2, 2, 2, 3, 2, 3, 1, 1, 3, 1, 4, 3, 1, 4, 3, 1, 2, 3, 3, 3, 3, 3, 3, 3, 2, 2, 3, 1, 1, 3, 1, 3, 3
OFFSET
2,3
COMMENTS
a(n) = A001221(A099909(n)).
LINKS
MATHEMATICA
dpf[{a_, b_}]:=PrimeNu[((a(b-1))+(a-1)b)/2]; dpf/@Partition[Prime[ Range[ 2, 110]], 2, 1] (* Harvey P. Dale, Nov 16 2011 *)
PROG
(PARI) a(n)=omega(((prime(n)*(prime(n+1)-1)+(prime(n)-1)*prime(n+1))/2)) \\ Michel Marcus, May 16 2017
CROSSREFS
Cf. A099911, A098142 (a(n) is 1).
Sequence in context: A362028 A303401 A327491 * A376780 A213325 A043555
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Oct 29 2004
STATUS
approved