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URL: https://oeis.org/A257848

⇱ A257848 - OEIS

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A257848
a(n) = floor(n/8) * (n mod 8).
1
0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 5, 6, 7, 0, 2, 4, 6, 8, 10, 12, 14, 0, 3, 6, 9, 12, 15, 18, 21, 0, 4, 8, 12, 16, 20, 24, 28, 0, 5, 10, 15, 20, 25, 30, 35, 0, 6, 12, 18, 24, 30, 36, 42, 0, 7, 14, 21, 28, 35, 42, 49, 0, 8, 16, 24, 32, 40, 48, 56, 0, 9
OFFSET
0,11
COMMENTS
Equivalently, write n in base 8, multiply the last digit by the number with its last digit removed.
LINKS
Index entries for linear recurrences with constant coefficients, signature (0,0,0,0,0,0,0,2,0,0,0,0,0,0,0,-1).
FORMULA
a(n) = 2*a(n-8)-a(n-16). - Colin Barker, May 11 2015
G.f.: x^9*(7*x^6+6*x^5+5*x^4+4*x^3+3*x^2+2*x+1) / ((x-1)^2*(x+1)^2*(x^2+1)^2*(x^4+1)^2). - Colin Barker, May 11 2015
MATHEMATICA
Table[Floor[n/8]Mod[n, 8], {n, 0, 90}] (* or *) LinearRecurrence[{0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, -1}, {0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 5, 6, 7}, 90] (* Harvey P. Dale, Nov 05 2023 *)
PROG
(PARI) a(n, b=8)=(n=divrem(n, b))[1]*n[2]
(PARI) concat([0, 0, 0, 0, 0, 0, 0, 0, 0], Vec(x^9*(7*x^6+6*x^5+5*x^4+4*x^3+3*x^2+2*x+1) / ((x-1)^2*(x+1)^2*(x^2+1)^2*(x^4+1)^2) + O(x^100))) \\ Colin Barker, May 11 2015
(Python)
def A257848(n): return (n>>3)*(n&7) # Chai Wah Wu, Jan 19 2023
CROSSREFS
Cf. A142150 (the base 2 analog), A115273, A257844 - A257850.
Sequence in context: A010877 A372352 A309959 * A195831 A265521 A004183
KEYWORD
nonn,base,easy
AUTHOR
M. F. Hasler, May 10 2015
STATUS
approved