OFFSET
1,1
COMMENTS
The records are: 4, 5, 7, 11, 19, 35, 67, ... and they occur at these indices of A014311: 11, 19, 35, 67, ... (for both, see A062709). - Michel Marcus, Jun 11 2015
The record (maximum) among the first 1000 terms is 65539. - Harvey P. Dale, May 29 2018
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
MATHEMATICA
Differences[Select[Range[500], DigitCount[#, 2, 1]==3&]] (* Harvey P. Dale, May 29 2018 *)
PROG
(JavaScript)
oo=0;
for (i=1; i<500; i++) {
s=i.toString(2);
o=0;
for (j=0; j<s.length; j++) if (s.charAt(j)==1) o++;
if (o==3) {document.write(i-oo+", "); oo=i; }
}
(PARI) lista(nn) = {my(last = 0); for (n=1, nn, if (hammingweight(n)==3, if (last, print1(n-last, ", ")); last = n; ); ); } \\ Michel Marcus, Jun 10 2015
(Python)
from math import isqrt, comb
from sympy import integer_nthroot
def A228132(n): return (1<<(r:=n-comb((m:=integer_nthroot(6*n+6, 3)[0])+(t:=(n>=comb(m+2, 3)))+1, 3))-comb((k:=isqrt(b:=r+1<<1))+(b>k*(k+1)), 2))+(1<<(a:=isqrt(s:=n+1-comb(m-(t^1)+2, 3)<<1))+((s<<2)>(a<<2)*(a+1)+1))+(1<<m+t+1)-(1<<(r:=n-1-comb((m:=integer_nthroot(6*n, 3)[0])+(t:=(n>comb(m+2, 3)))+1, 3))-comb((k:=isqrt(b:=r+1<<1))+(b>k*(k+1)), 2))-(1<<(a:=isqrt(s:=n-comb(m-(t^1)+2, 3)<<1))+((s<<2)>(a<<2)*(a+1)+1))-(1<<m+t+1) # Chai Wah Wu, Apr 07 2025
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Jon Perry, Nov 02 2013
STATUS
approved
