A197357 Number of n-digits integers for which the sum of the odd-positioned digits equals the sum of the even-positioned digits.

1, 10, 55, 670, 4840, 55252, 436975, 4816030, 40051495, 432457640, 3715101654, 39581170420, 347847754670, 3671331273480, 32811494188975, 343900019857310, 3113537578058979, 32458256583753952, 296896918816556380, 3081918923741896840

Offset: 1

Author

Colin Barker, Oct 13 2011

Keywords

• nonn
• base

Comments

a(n) is the number of n-digit integers such that the sum of the odd-positioned digits is equal to the sum of the even-positioned digits, leading zeros being allowed in the integers.

Examples

			The number 28754 is one of the 4840 5-digit numbers because 2+7+4 = 8+5.
		

Links

• Colin Barker, Table of n, a(n) for n = 1..200

Crossrefs

This sequence has some numbers in common with both A025015 and A174061. In fact, A174061 consists of the elements a(2n), and the elements a(2n) are all elements of A025015.

Programs

PARI

a(n) = {nb = 0; for (i=0, 10^n-1, digs = digits(i, 10); while(#digs != n, digs = concat(0, digs)); so = 0; forstep(j=1, n, 2, so += digs[j]); se = 0; forstep(j=2, n, 2, se += digs[j]); if (se == so, nb++);); return (nb);} \\ Michel Marcus, Jun 08 2013