A317395 Positive integers that have exactly five representations of the form 1 + p1 * (1 + p2* ... * (1 + p_j)...), where [p1, ..., p_j] is a (possibly empty) list of distinct primes.

638, 848, 921, 969, 1002, 1026, 1106, 1156, 1191, 1248, 1276, 1310, 1326, 1341, 1431, 1444, 1480, 1499, 1548, 1592, 1641, 1730, 1764, 1772, 1786, 1856, 1888, 1911, 1996, 2005, 2025, 2038, 2050, 2053, 2061, 2121, 2129, 2131, 2133, 2146, 2171, 2224, 2256, 2258

Offset

1,1

Links

Alois P. Heinz, Table of n, a(n) for n = 1..20000

Formula

A317241(a(n)) = 5.

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<6
        do r:= r+b((n-1)/p, s union {p}) od; `if`(r<6, r, 6)
      fi
    end:
a:= proc(n) option remember; local k; for k from
     `if`(n=1, 1, 1+a(n-1)) while b(k, {})<>5 do od; k
    end:
seq(a(n), n=1..100);

Crossrefs

Column k=5 of A317390.

Cf. A317241.

Sequence in context: A203880 A250465 A203879 * A212399 A264449 A210883

Adjacent sequences: A317392 A317393 A317394 * A317396 A317397 A317398

Keyword

nonn

Author

Alois P. Heinz, Jul 27 2018

Status

approved