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A317391
Positive integers that have a unique representation of the form 1 + p1 * (1 + p2* ... * (1 + p_j)...), where [p1, ..., p_j] is a (possibly empty) list of distinct primes.
2
1, 3, 4, 6, 8, 9, 10, 12, 13, 14, 16, 17, 18, 19, 20, 21, 22, 24, 30, 32, 34, 38, 39, 42, 44, 45, 46, 48, 53, 54, 55, 58, 59, 60, 62, 64, 65, 68, 69, 70, 72, 73, 74, 75, 76, 79, 80, 83, 84, 86, 90, 92, 93, 94, 98, 99, 100, 101, 102, 104, 105, 107, 108, 109
OFFSET
1,2
LINKS
FORMULA
A317241(a(n)) = 1.
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<2
do r:= r+b((n-1)/p, s union {p}) od; `if`(r<2, r, 2)
fi
end:
a:= proc(n) option remember; local k; for k from
`if`(n=1, 1, 1+a(n-1)) while b(k, {})<>1 do od; k
end:
seq(a(n), n=1..100);
CROSSREFS
Column k=1 of A317390.
Cf. A317241.
Sequence in context: A090864 A118300 A263098 * A134745 A183867 A182829
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Jul 27 2018
STATUS
approved