A273416 Numbers that occur 5 or more times in the triangle of denominators in Leibniz's Harmonic Triangle.

30, 1260, 1980, 74256, 1861860, 603380175840

Offset

1,1

Comments

Of the first 6 terms the number 30 occurs 5 times, the others occur 6 times.

a(6) = 603380175840 is not an oblong number.

Links

Table of n, a(n) for n=1..6.

Example

The number 30 appears 1 time in row 5 in the central position {5*C(4,2)}, 2 times in row 6 {6*C(5,1); 6*C(5,4)} and, trivially, 2 times in row 30 {30*C(29,0); 30*C(29,29)}.
The number 1260 appears 2 times in row 10 {10*C(9,4); 10*C(9,5)}, 2 times in row 36 {36*C(35,1); 36*C(35,34)} and, trivially, 2 times in row 1260 {1260*C(1259,0); 1260*C(1259,1259)}.

Crossrefs

Cf. A003506.

Sequence in context: A060076 A174716 A163521 * A002456 A358163 A107768

Adjacent sequences: A273413 A273414 A273415 * A273417 A273418 A273419

Keyword

nonn,more

Author

Gionata Neri, May 22 2016

Status

approved