A284972 Numbers with digits 4 and 8 only.

4, 8, 44, 48, 84, 88, 444, 448, 484, 488, 844, 848, 884, 888, 4444, 4448, 4484, 4488, 4844, 4848, 4884, 4888, 8444, 8448, 8484, 8488, 8844, 8848, 8884, 8888, 44444, 44448, 44484, 44488, 44844, 44848, 44884, 44888, 48444, 48448, 48484, 48488, 48844, 48848

Offset

1,1

Comments

All terms are even.

Links

Table of n, a(n) for n=1..44.

Formula

a(n) = 2 * A284920(n) = 4 * A032822(n).

Mathematica

Flatten@ Table[FromDigits /@ Tuples[{4, 8}, n], {n, 5}] (* Giovanni Resta, Apr 07 2017 *)

Prog

(Magma) [n: n in [1..100000] | Set(IntegerToSequence(n, 10)) subset {4, 8}]
(PARI) a(n) = my (b = binary(1+n)); b[1] = 0; return (4*(10^(#b-1)-1)/(10-1) + (8-4)*fromdigits(b)) \\ Rémy Sigrist, Apr 08 2017
(PARI) a(n)={my(v=binary(n+1)); v[1]=0; v+=vector(#v, i, i>1); 4*fromdigits(v)} \\ R. J. Cano, Apr 08 2017
(PARI) a(n, {p=[4, 8]})={my(v=binary(n+1)); fromdigits(vector(#v-1, i, p[2]*v[i+1]+p[1]*!v[i+1]))} \\ R. J. Cano, Apr 09 2017

Crossrefs

Numbers with digits 4 and k only for k = 0 - 3 and 5 - 9: A169967 (k = 0), A032822 (k = 1), A284920 (k = 2), A032834 (k = 3), A256290 (k = 5), A284634 (k = 6), A284971 (k = 7), this sequence (k = 8), A284973 (k = 9).

Sequence in context: A137054 A338423 A163343 * A045639 A337782 A285751

Adjacent sequences: A284969 A284970 A284971 * A284973 A284974 A284975

Keyword

nonn,base

Author

Jaroslav Krizek, Apr 07 2017

Status

approved