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A117583 For successive primes p, the number of ratios t(n)/(t(n)-1), where t(n)=n(n+1)/2 is the n-th triangular number, which factor into primes less than or equal to p. 2
0, 1, 3, 7, 9, 16, 22, 29, 35, 39, 50, 57, 68 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

As in the case of square numerators, triangular numerators of superparticular ratios m/(m-1) factorizable only up to a relatively small prime p are relatively common.

REFERENCES

E. F. Ecklund and R. B. Eggleton, Prime factors of consecutive integers, Amer. Math. Monthly, 79 (1972), 1082-1089.

D. H. Lehmer, On a problem of Stormer, Ill. J. Math., 8 (1964), 57-69.

LINKS

Table of n, a(n) for n=1..13.

CROSSREFS

Cf. A002071, A117582.

Sequence in context: A192118 A057463 A118258 * A126106 A064194 A036978

Adjacent sequences:  A117580 A117581 A117582 * A117584 A117585 A117586

KEYWORD

hard,nonn

AUTHOR

Gene Ward Smith, Apr 02 2006

STATUS

approved

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Last modified April 16 21:07 EDT 2014. Contains 240627 sequences.