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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

Amiram Eldar, Table of n, a(n) for n = 1..10000

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

Cf. A001221, A104186.

Sequence in context: A079643 A329317 A118480 * A109337 A303539 A303540

Adjacent sequences:  A104374 A104375 A104376 * A104378 A104379 A104380

KEYWORD

nonn,base

AUTHOR

Parthasarathy Nambi, Apr 16 2005

EXTENSIONS

Offset corrected and more terms added by Amiram Eldar, Jan 27 2020

STATUS

approved

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Last modified May 16 12:46 EDT 2021. Contains 343947 sequences. (Running on oeis4.)