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A317396
Positive integers that have exactly six representations of the form 1 + p1 * (1 + p2* ... * (1 + p_j)...), where [p1, ..., p_j] is a (possibly empty) list of distinct primes.
2
664, 1956, 2058, 2092, 2094, 2283, 2381, 2388, 2432, 2466, 2533, 2624, 2701, 2775, 2822, 2853, 2976, 3070, 3193, 3220, 3316, 3326, 3436, 3442, 3461, 3485, 3529, 3568, 3571, 3576, 3620, 3746, 3784, 3785, 3797, 3826, 3839, 3913, 4005, 4026, 4031, 4213, 4234
OFFSET
1,1
LINKS
FORMULA
A317241(a(n)) = 6.
MAPLE
b:= proc(n, s) option remember; local p, r; if n=1 then 1 else r:=0;
for p in numtheory[factorset](n-1) minus s while r<7
do r:= r+b((n-1)/p, s union {p}) od; `if`(r<7, r, 7)
fi
end:
a:= proc(n) option remember; local k; for k from
`if`(n=1, 1, 1+a(n-1)) while b(k, {})<>6 do od; k
end:
seq(a(n), n=1..100);
CROSSREFS
Column k=6 of A317390.
Cf. A317241.
Sequence in context: A243889 A105978 A208180 * A211839 A171395 A069426
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Jul 27 2018
STATUS
approved