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A249224
Lpf (n(n+11)/2): least prime dividing n(n+11)/2.
1
2, 13, 3, 2, 2, 3, 3, 2, 2, 3, 11, 2, 2, 5, 3, 2, 2, 3, 3, 2, 2, 3, 17, 2, 2, 13, 3, 2, 2, 3, 3, 2, 2, 3, 5, 2, 2, 7, 3, 2, 2, 3, 3, 2, 2, 3, 29, 2, 2, 5, 3, 2, 2, 3, 3, 2, 2, 3, 5, 2, 2, 31, 3, 2, 2, 3, 3, 2, 2, 3, 41, 2, 2, 5, 3, 2, 2, 3, 3, 2, 2, 3, 47, 2, 2, 43, 3, 2, 2, 3, 3, 2, 2, 3, 5, 2, 2, 7, 3, 2
OFFSET
1,1
COMMENTS
a(n) = 2 for n = {4,5,8,9} (mod 12) and a(n) = 3 for n = {3,6,7,10} (mod 12).
FORMULA
a(n) = A020639(n(n+11)/2).
MATHEMATICA
FactorInteger[#(11+#)/2][[1, 1]]& /@ Range[100]
PROG
(PARI) a(n) = my(f=factor(n*(n+11)/2)); f[1, 1]; \\ Michel Marcus, Oct 23 2014
CROSSREFS
Sequence in context: A090954 A089778 A088253 * A217010 A091023 A337838
KEYWORD
nonn,easy
AUTHOR
Zak Seidov, Oct 23 2014
STATUS
approved