A317397 Positive integers that have exactly seven representations of the form 1 + p1 * (1 + p2* ... * (1 + p_j)...), where [p1, ..., p_j] is a (possibly empty) list of distinct primes.
1613, 3321, 3336, 3368, 3741, 3914, 3979, 4082, 4126, 4219, 4561, 4777, 4798, 4824, 4929, 4936, 4948, 5083, 5314, 5371, 5559, 5656, 5825, 5877, 5946, 5986, 6096, 6109, 6111, 6291, 6303, 6376, 6644, 6651, 6673, 6700, 6711, 6786, 6883, 6886, 6917, 6920, 7036
Offset: 1
Keywords
Links
- Alois P. Heinz, Table of n, a(n) for n = 1..20000
Programs
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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<8 do r:= r+b((n-1)/p, s union {p}) od; `if`(r<8, r, 8) fi end: a:= proc(n) option remember; local k; for k from `if`(n=1, 1, 1+a(n-1)) while b(k, {})<>7 do od; k end: seq(a(n), n=1..100);
Formula
A317241(a(n)) = 7.