A284973 - OEIS

A284973

Numbers with digits 4 and 9 only.

4, 9, 44, 49, 94, 99, 444, 449, 494, 499, 944, 949, 994, 999, 4444, 4449, 4494, 4499, 4944, 4949, 4994, 4999, 9444, 9449, 9494, 9499, 9944, 9949, 9994, 9999, 44444, 44449, 44494, 44499, 44944, 44949, 44994, 44999, 49444, 49449, 49494, 49499, 49944, 49949

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OFFSET

1,1

LINKS

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

PROG

(Magma) [n: n in [1..100000] | Set(IntegerToSequence(n, 10)) subset {4, 9}]

(PARI) a(n, {p=[4, 9]})={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

Prime terms are in A020466.

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), A284972 (k = 8), this sequence (k = 9).

Sequence in context: A359922 A093149 A048054 * A239853 A209079 A149170

Adjacent sequences: A284970 A284971 A284972 * A284974 A284975 A284976

KEYWORD

nonn,base

AUTHOR

Jaroslav Krizek, Apr 07 2017

STATUS

approved