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A055600 Numbers of form 2^i*3^j+1 with i, j >= 0. 13
2, 3, 4, 5, 7, 9, 10, 13, 17, 19, 25, 28, 33, 37, 49, 55, 65, 73, 82, 97, 109, 129, 145, 163, 193, 217, 244, 257, 289, 325, 385, 433, 487, 513, 577, 649, 730, 769, 865, 973, 1025, 1153, 1297, 1459, 1537, 1729, 1945, 2049, 2188, 2305, 2593, 2917, 3073, 3457, 3889 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

If X is an n-set and Y a fixed (n-5)-subset of X then a(n-5) is equal to the number of 2-subsets of X intersecting Y. - Milan Janjic, Aug 15 2007

REFERENCES

G. Everest, P. Rogers and T. Ward, A higher-rank Mersenne problem, pp. 95-107 of ANTS 2002, Lect. Notes Computer Sci. 2369 (2002).

LINKS

Table of n, a(n) for n=0..54.

Milan Janjic, Two Enumerative Functions

FORMULA

a(n)=A003586(n)+1

EXAMPLE

a(7)=13 since 13=2^2*3^1+1

MATHEMATICA

mx = 4000; Sort@ Flatten@ Table[ 2^i*3^j + 1, {i, 0, Log[2, mx]}, {j, 0, Log[3, mx/2^i]}] (* Robert G. Wilson v, Aug 17 2012 *)

CROSSREFS

Primes in this sequence give A005109 (Class 1- or Pierpoint primes).

Sequence in context: A060526 A036408 A274583 * A139528 A178434 A267439

Adjacent sequences:  A055597 A055598 A055599 * A055601 A055602 A055603

KEYWORD

easy,nonn

AUTHOR

Henry Bottomley, Jun 01 2000

STATUS

approved

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Last modified September 20 12:42 EDT 2017. Contains 292271 sequences.