A277694 - OEIS

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A277694

Numbers which cannot occur in A277623, where any odd digit d must be followed by d even digits.

11, 13, 15, 17, 19, 31, 33, 35, 37, 39, 51, 53, 55, 57, 59, 71, 73, 75, 77, 79, 91, 93, 95, 97, 99, 100, 102, 104, 106, 108, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 122, 124, 126, 128, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 142, 144, 146, 148, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 162, 164, 166, 168, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 182, 184, 186, 188

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OFFSET

1,1

COMMENTS

Any number which contains a term of this sequence as a substring is again in this sequence. Therefore one might call those terms of this sequence which do not contain a smaller term as a substring "primitive". The non-primitive terms are 110 - 119, 130 - 139, ..., 211, 213, 215, etc.

LINKS

Table of n, a(n) for n=1..90.

EXAMPLE

Any digit '1' must be followed by exactly one even digit if the number is in A277623. Therefore 11, 13, 17, 19 (and any number which contains these, such as 110 or 211), and also 100, 102, ... are not allowed there and are thus listed here.

Similarly, any digit '3' must be followed by exactly three even digits in A277623. Therefore 31, 33, 37, 39, and also 301, 303, ... cannot appear there and are listed here.

PROG

(PARI) select( is(n, c=-1)=for(i=1, #n=digits(n), if(bittest(n[i], 0), c<=0&&c=n[i], c--!=-1)||return(1)), [0..199])

CROSSREFS

Cf. A277623.

Sequence in context: A277268 A337254 A152200 * A179084 A375967 A124569

Adjacent sequences: A277691 A277692 A277693 * A277695 A277696 A277697

KEYWORD

nonn,base,easy

AUTHOR

M. F. Hasler, Oct 27 2016

STATUS

approved