login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A101278 Write n in base 3 as n = b_0 + b_1*3 + b_2*3^2 + b_3*3^3 + ...; then a(n) = Product_{i >= 0} prime(i+1)^b_i. 5
1, 2, 4, 3, 6, 12, 9, 18, 36, 5, 10, 20, 15, 30, 60, 45, 90, 180, 25, 50, 100, 75, 150, 300, 225, 450, 900, 7, 14, 28, 21, 42, 84, 63, 126, 252, 35, 70, 140, 105, 210, 420, 315, 630, 1260, 175, 350, 700, 525, 1050, 2100, 1575, 3150, 6300, 49, 98, 196, 147, 294, 588 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

One may generate other sequences by changing the base b.

LINKS

R. Zumkeller, Table of n, a(n) for n = 0..6560

FORMULA

If a(bn)=x then a(bn+1)=2x, a(bn+2)=4x, ... a(bn+b-1)=2^b*x. - Robert G. Wilson v, Dec 24 2004

G.f.: (1+2x+4x^2)(1+3x^3+9x^6)(1+5x^9+25x^18)... - Paul Boddington, Jul 21 2005

a(n) = f(n, 1, 1) with f(x, y, z) = if x > 0 then f(floor(x/3), y*prime(z)^(x mod 3), z+1) else y. - Reinhard Zumkeller, Mar 13 2010

EXAMPLE

The first few terms are computed as follows:

  n b2 b1 b0 a(n)

  0, 0, 0, 0,  1

  1, 0, 0, 1,  2

  2, 0, 0, 2,  4

  3, 0, 1, 0,  3

  4, 0, 1, 1,  6

  5, 0, 1, 2, 12

MATHEMATICA

primeBase[n_Integer?Positive, base_Integer]/; base>1 := Times @@ (Table[Prime[i], {i, Floor[Log[base, n] + 1], 1, -1}]^IntegerDigits[n, base]); Table[primeBase[n, 3], {n, 59}] (* Robert G. Wilson v, Dec 24 2004 *)

CROSSREFS

Cf. A019565, A054842. - Reinhard Zumkeller, Mar 13 2010

Sequence in context: A222600 A046793 A182940 * A091274 A122525 A054589

Adjacent sequences:  A101275 A101276 A101277 * A101279 A101280 A101281

KEYWORD

nonn,easy

AUTHOR

Orges Leka (oleka(AT)students.uni-mainz.de), Dec 20 2004

EXTENSIONS

More terms from Robert G. Wilson v, Dec 24 2004

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 18 12:18 EDT 2019. Contains 328160 sequences. (Running on oeis4.)