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A014312 Numbers with exactly 4 ones in binary expansion. 15
15, 23, 27, 29, 30, 39, 43, 45, 46, 51, 53, 54, 57, 58, 60, 71, 75, 77, 78, 83, 85, 86, 89, 90, 92, 99, 101, 102, 105, 106, 108, 113, 114, 116, 120, 135, 139, 141, 142, 147, 149, 150, 153, 154, 156, 163, 165, 166, 169, 170, 172, 177, 178, 180, 184, 195, 197 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

T. D. Noe and Ivan Neretin, Table of n, a(n) for n = 1..10000 [terms 1..1000 from T. D. Noe]

FORMULA

a(n+1) = A057168(a(n)). - M. F. Hasler, Aug 27 2014

MATHEMATICA

Select[ Range[ 180 ], (Count[ IntegerDigits[ #, 2 ], 1 ]==4)& ] (* Olivier Gérard *)

PROG

(Perl) $N = 4;

my $vector = 2 ** $N - 1;  # first key (15)

for (1..100) {

  print "$vector, ";

  my ($v, $d) = ($vector, 0);

  until ($v & 1 or !$v) { $d = ($d << 1)|1; $v >>= 1 }

  $vector += $d + 1 + (($v ^ ($v + 1)) >> 2);  # next key

} # Ruud H.G. van Tol, Mar 02 2014

(PARI) for(n=0, 10^3, if(hammingweight(n)==4, print1(n, ", "))); \\ Joerg Arndt, Mar 04 2014

(PARI) print1(t=15); for(i=2, 50, print1(", "t=A057168(t))) \\ M. F. Hasler, Aug 27 2014

CROSSREFS

Cf. A090706.

Cf. A000079, A018900, A014311, A014312, A014313, A023688, A023689, A023690, A023691 (Hamming weight = 1, 2, ..., 9), A057168.

Sequence in context: A241253 A219683 A166665 * A129387 A171167 A242412

Adjacent sequences:  A014309 A014310 A014311 * A014313 A014314 A014315

KEYWORD

nonn,base,easy

AUTHOR

Al Black (gblack(AT)nol.net)

EXTENSIONS

Extension by Olivier Gérard

STATUS

approved

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Last modified August 21 00:43 EDT 2017. Contains 290855 sequences.