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URL: https://oeis.org/A048440

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A048440
Take the first n numbers written in base 8, concatenate them, then convert from base 8 to base 10.
17
1, 10, 83, 668, 5349, 42798, 342391, 21913032, 1402434057, 89755779658, 5744369898123, 367639673479884, 23528939102712589, 1505852102573605710, 96374534564710765455, 6167970212141488989136, 394750093577055295304721, 25264005988931538899502162
OFFSET
1,2
COMMENTS
83 is the only prime in this sequence among the first 3000 terms (email from Kurt Foster, Oct 24 2015). - N. J. A. Sloane, Oct 25 2015
LINKS
EXAMPLE
a(9): (1)(2)(3)(4)(5)(6)(7)(10)(11) = 12345671011_8 = 1402434057.
MATHEMATICA
If[STARTPOINT==1, n={}, n=Flatten[IntegerDigits[Range[STARTPOINT-1], 8]]]; Table[AppendTo[n, IntegerDigits[w, 8]]; n=Flatten[n]; FromDigits[n, 8], {w, STARTPOINT, ENDPOINT}] (* Dylan Hamilton, Aug 11 2010 *)
Table[FromDigits[Flatten[IntegerDigits[#, 8]&/@Range[n]], 8], {n, 20}] (* Harvey P. Dale, Dec 07 2012 *)
PROG
(Magma) [n eq 1 select 1 else Self(n-1)*8^(1+Ilog(8, n))+n: n in [1..20]]; // Vincenzo Librandi, Dec 30 2012
(Python)
from functools import reduce
def A048440(n): return reduce(lambda i, j:(i<<3*(1+(j.bit_length()-1)//3))+j, range(n+1)) # Chai Wah Wu, Feb 26 2023
CROSSREFS
Cf. A014831.
Concatenation of first n numbers in other bases: 2: A047778, 3: A048435, 4: A048436, 5: A048437, 6: A048438, 7: A048439, 8: this sequence, 9: A048441, 10: A007908, 11: A048442, 12: A048443, 13: A048444, 14: A048445, 15: A048446, 16: A048447.
Sequence in context: A037608 A055149 A014831 * A226202 A271557 A351750
KEYWORD
nonn,base,easy
AUTHOR
Patrick De Geest, May 15 1999
STATUS
approved