

A280878


Occurrences of decrease of the probability density P(n) of coprime numbers k,m, satisfying 1 <= k <= a(n) and 1 <= m <= a(n), and a(n) congruent to 1(mod 2) and a(n) congruent to {3,9,21,27}(mod 30).


3



21, 33, 63, 99, 147, 189, 231, 273, 297, 357, 363, 399, 429, 441, 483, 561, 567, 609, 627, 651, 663, 693, 741, 759, 777, 819, 861, 891, 897, 903, 957, 969, 987, 1023, 1029, 1071, 1089, 1113, 1131, 1173, 1197, 1209, 1221, 1239, 1281, 1287, 1311, 1323, 1353, 1407, 1419, 1443, 1449
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OFFSET

1,1


COMMENTS

Probability densities satisfying P(a(n)) < P(a(n)1) and 1 <= m <= a(n), and a(n) congruent to 1(mod 2) and a(n) congruent to {3,9,21,27}(mod 30).
Subset of A280877.
Related to Euler phi function A000010 by P(n) = ((2*Sum_{m=1..a(n)} phi(m))1)/a(n)^2.


LINKS

A.H.M. Smeets, Table of n, a(n) for n = 1..11142


PROG

(Python)
from fractions import gcd
t = 1
to = 1
i = 1
x = 1
while x > 0:
....x = x + 1
....y = 0
....while y < x:
........y = y + 1
........if gcd(x, y) == 1:
............t = t + 2
....e = t*(x1)*(x1)  to*x*x
....if (e < 0 and x%2 == 1 and x%6 == 3 and x%30 != 15):
........print(i, x)
........i = i + 1
....to = t


CROSSREFS

Sequence in context: A032603 A233562 A128283 * A033901 A033656 A270074
Adjacent sequences: A280875 A280876 A280877 * A280879 A280880 A280881


KEYWORD

nonn


AUTHOR

A.H.M. Smeets, Jan 09 2017


STATUS

approved



