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A336964
Irregular triangle in which first row is 1, n-th row (n > 1) lists distinct prime numbers in the prime tower factorization of n.
2
1, 2, 3, 2, 5, 2, 3, 7, 2, 3, 2, 3, 2, 5, 11, 2, 3, 13, 2, 7, 3, 5, 2, 17, 2, 3, 19, 2, 5, 3, 7, 2, 11, 23, 2, 3, 2, 5, 2, 13, 3, 2, 7, 29, 2, 3, 5, 31, 2, 5, 3, 11, 2, 17, 5, 7, 2, 3, 37, 2, 19, 3, 13, 2, 3, 5, 41, 2, 3, 7, 43, 2, 11, 2, 3, 5, 2, 23, 47, 2, 3
OFFSET
1,2
COMMENTS
The prime tower factorization of a number is defined in A182318.
The n-th row includes the n-th row of A027748.
LINKS
Rémy Sigrist, Table of n, a(n) for n = 1..10001 (rows for n = 1..4045)
EXAMPLE
Triangle begins:
1 [1]
2 [2]
3 [3]
4 [2]
5 [5]
6 [2, 3]
7 [7]
8 [2, 3]
9 [2, 3]
10 [2, 5]
11 [11]
12 [2, 3]
13 [13]
14 [2, 7]
15 [3, 5]
PROG
(PARI) row(n) = { my (f=factor(n), p=f[, 1]~); for (k=1, #f~, if (f[k, 2]>1, p=concat(p, row(f[k, 2]))); ); if (#p==0, [1], Set(p)) }
CROSSREFS
Cf. A027748, A115588 (row lengths), A182318, A336965.
Sequence in context: A129088 A086418 A100761 * A027748 A361650 A328852
KEYWORD
nonn,tabf
AUTHOR
Rémy Sigrist, Aug 09 2020
STATUS
approved