cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-2 of 2 results.

A065025 Consider biquanimous numbers that exclude 0's; sequence gives number of n-digit non-biquanimous numbers - number of n-digit biquanimous numbers.

Original entry on oeis.org

9, 63, 513, 3423, 18589, 73035, 225479, 617215, 1622001, 4300263, 12128763, 37076783, 122411649, 427600575, 1550703157, 5759666431, 21738733961, 82999762711, 319722139579, 1240393764207, 4840363237201, 18979321319087, 74713018378209, 295061102101311
Offset: 1

Views

Author

N. J. A. Sloane, Nov 03 2001

Keywords

Comments

A biquanimous number (A064544) is a number whose digits can be split into two groups with equal sums.

References

Crossrefs

Formula

From Alois P. Heinz, Jun 12 2017: (Start)
G.f.: -x*(988416*x^33 +272448*x^32 -6983328*x^31 -2873424*x^30 +20931912*x^29 +11886288*x^28 -33545700*x^27 -25677164*x^26 +28467368*x^25 +29854804*x^24 -7032026*x^23 -11748538*x^22 -12593064*x^21 -17118040*x^20 +24399398*x^19 +29412358*x^18 -32880510*x^17 -15770937*x^16 +33016792*x^15 -4824040*x^14 -21307320*x^13 +10258240*x^12 +7474762*x^11 -5162898*x^10 -999324*x^9 +1008806*x^8 +39654*x^7 -89810*x^6 +3200*x^5 +992*x^4 +1248*x^3 -468*x^2 +90*x -9) / ((4*x-1) *(3*x-1)^2 *(2*x-1)^3 *(x+1)^7 *(x-1)^8).
a(n) = 9^n - 2 * A288550(n). (End)

Extensions

New offset and 4 more terms from Alois P. Heinz, Jun 11 2017

A288352 Number of strings of n digits from 1..9 such that a formula using the single digits in the given order with result 0 needs at least one division.

Original entry on oeis.org

0, 0, 5, 168, 659, 163, 14, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
Offset: 1

Views

Author

Hugo Pfoertner, Jun 10 2017

Keywords

Comments

For definitions see A288350. An exhaustive computation for the 9^8 strings of 8 digits confirms that for all of them formulas avoiding divisions exist. a(8) = 0 implies that a(n) = 0 for n > 8.

Examples

			a(3)=5, because the 5 3-digit strings 263 (0=2-6/3), 284 (0=2-8/4), 362 (0=3-6/2), 393 (3-9/3), 482 (0=4-8/2) are the only ones of the 9^3-A288351(3)=274 3-digit strings for which a formula with result 0 exists that cannot avoid including a division.
A288502 provides a list of all strings with this property.
		

Crossrefs

Showing 1-2 of 2 results.