|
|
A104377
|
|
Number of distinct prime divisors of numbers derived from three consecutive concatenated odd numbers.
|
|
2
|
|
|
2, 3, 2, 2, 3, 4, 2, 3, 3, 2, 4, 2, 2, 2, 2, 4, 3, 3, 2, 2, 4, 3, 3, 3, 2, 5, 3, 2, 3, 3, 3, 3, 2, 2, 2, 3, 2, 3, 3, 3, 3, 3, 3, 3, 2, 3, 3, 3, 4, 2, 4, 4, 4, 3, 3, 4, 2, 3, 4, 3, 4, 3, 3, 3, 3, 5, 3, 4, 2, 2, 6, 3, 3, 4, 3, 3, 3, 3, 3, 3, 3, 5, 3, 4, 4, 4, 5
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
LINKS
|
|
|
EXAMPLE
|
The number of distinct prime divisors of 135 is 2 - the first term in the sequence.
The number of distinct prime divisors of 357 is 3 - the second term in the sequence.
The number of distinct prime divisors of 579 is 2 - the third term in the sequence.
|
|
MAPLE
|
read("transforms") :
A104377 := proc(n) digcat2(digcat2(2*n+1, 2*n+3), 2*n+5) ; nops(numtheory[factorset](%)) ; end proc: # R. J. Mathar, Feb 03 2011
|
|
MATHEMATICA
|
a[n_] := PrimeNu@ FromDigits@(Join @@ IntegerDigits /@ (2*n + {-1, 1, 3})); Array[a, 100] (* Amiram Eldar, Jan 27 2020 *)
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,base
|
|
AUTHOR
|
|
|
EXTENSIONS
|
Offset corrected and more terms added by Amiram Eldar, Jan 27 2020
|
|
STATUS
|
approved
|
|
|
|