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URL: https://oeis.org/A392232

⇱ A392232 - OEIS

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A392232
Numbers k for which omega(k)*omega(k + 1)*omega(k + 2)*omega(k + 3)*omega(k + 4) = 4 where omega = A001221.
3
6, 8, 9, 13, 15, 16, 23, 25, 79
OFFSET
1,1
COMMENTS
Probably finite.
EXAMPLE
k | omega(k)*omega(k + 1)*omega(k + 2)*omega(k + 3)*omega(k + 4)
----------------------------------------------------------------------
6 | 2 * 1 * 1 * 1 * 2 = 4;
8 | 1 * 1 * 1 * 2 * 2 = 4;
9 | 1 * 2 * 1 * 2 * 1 = 4;
13 | 1 * 2 * 2 * 1 * 1 = 4;
15 | 2 * 1 * 1 * 2 * 1 = 4;
16 | 1 * 1 * 2 * 1 * 2 = 4;
23 | 1 * 2 * 1 * 2 * 1 = 4;
25 | 1 * 2 * 1 * 2 * 1 = 4;
79 | 1 * 2 * 1 * 2 * 1 = 4.
PROG
(Magma) [k: k in [1..10^6] | #PrimeDivisors(k)*#PrimeDivisors(k+1)*#PrimeDivisors(k+2)*#PrimeDivisors(k+3)*#PrimeDivisors(k+4) eq 4];
CROSSREFS
Numbers k for which omega(k)*omega(k + 1)* ... *omega(k + n) = n are 1 (in case n = 0); A006549 (n = 1); A391044 (n = 2); 29, 125, ... (n = 3); this sequence (n = 4).
Sequence in context: A191980 A304412 A161982 * A285275 A117096 A067812
KEYWORD
nonn,more
AUTHOR
STATUS
approved