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A044631 Numbers n such that string 7,7 occurs in the base 8 representation of n but not of n+1. 1
63, 127, 191, 255, 319, 383, 447, 511, 575, 639, 703, 767, 831, 895, 959, 1023, 1087, 1151, 1215, 1279, 1343, 1407, 1471, 1535, 1599, 1663, 1727, 1791, 1855, 1919, 1983, 2047, 2111, 2175, 2239, 2303, 2367, 2431, 2495, 2559, 2623, 2687, 2751, 2815, 2879, 2943 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
Tanya Khovanova, Non Recursions
MATHEMATICA
f[n_] := Length[StringPosition[ToString[FromDigits[IntegerDigits[n, 8]]], "77", 1]]; a1 = Select[Table[n, {n, 10000}], f[#] > 0 && f[# + 1] == 0 &] (* Vladimir Joseph Stephan Orlovsky, Jul 14 2011 *)
PROG
(PARI) has77(n)=my(t); while(n, if(bitand(n, 7)==7, if(t, return(1), t=1), t=0); n>>=3); 0
is(n)=has77(n)&&!has77(n+1) \\ Charles R Greathouse IV, Jul 14 2011
CROSSREFS
Sequence in context: A043450 A031491 A044250 * A045136 A031895 A044314
KEYWORD
nonn,base
AUTHOR
STATUS
approved

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Last modified May 19 14:45 EDT 2024. Contains 372698 sequences. (Running on oeis4.)