A061873 Numbers n such that |first digit - second digit + third digit - fourth digit ...| = 4.

4, 15, 26, 37, 40, 48, 51, 59, 62, 73, 84, 95, 103, 114, 125, 136, 147, 150, 158, 161, 169, 172, 183, 194, 202, 213, 224, 235, 246, 257, 260, 268, 271, 279, 282, 293, 301, 312, 323, 334, 345, 356, 367, 370, 378, 381, 389, 392, 400, 411, 422, 433, 444, 455

Offset: 1

Author

Robert G. Wilson v, May 10 2001

Keywords

• nonn
• base
• easy

Comments

All terms == 4 or 7 (mod 11). - Robert Israel, Jun 03 2016

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A008593, A060978-A060980, A060982, A061470-A061479, A061870-A061882.

Programs

Maple

F:= proc(n) option remember;
      -procname(floor(n/10)) + (n mod 10)
    end proc:
for j from 0 to 9 do F(j):= j od:
select(abs @ F = 4, [$1..1000]); # Robert Israel, Jun 03 2016

Mathematica

Do[ a = IntegerDigits[ n ]; l = Length[ a ]; e = o = {}; Do[ o = Append[ o, a[ [ 2k - 1 ] ] ], {k, 1, l/2 + .5} ]; Do[ e = Append[ e, a[ [ 2k ] ] ], {k, 1, l/2} ]; If[ Abs[ Apply[ Plus, o ] - Apply[ Plus, e ] ] == 4, Print[ n ] ], {n, 1, 1000} ]

Python

def ok(n): return abs(sum((-1)**i*int(d) for i, d in enumerate(str(n))))==4
print(list(filter(ok, range(456)))) # Michael S. Branicky, Apr 15 2021