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A069534
Smallest multiple of 5 with digit sum n.
15
10, 20, 30, 40, 5, 15, 25, 35, 45, 55, 65, 75, 85, 95, 195, 295, 395, 495, 595, 695, 795, 895, 995, 1995, 2995, 3995, 4995, 5995, 6995, 7995, 8995, 9995, 19995, 29995, 39995, 49995, 59995, 69995, 79995, 89995, 99995, 199995, 299995, 399995, 499995, 599995
OFFSET
1,1
COMMENTS
a(6) onwards the pattern is evident.
FORMULA
a(n) = ((n+4)%9+1)*10^floor((n+4)/9)-5 for all n > 4, where % is the binary mod/remainder operator. - M. F. Hasler, Sep 16 2016
From Chai Wah Wu, Sep 15 2020: (Start)
a(n) = a(n-1) + 10*a(n-9) - 10*a(n-10) for n > 14.
G.f.: 5*x*(72*x^13 - 18*x^12 - 18*x^11 - 18*x^10 - 18*x^9 + 2*x^8 + 2*x^7 + 2*x^6 + 2*x^5 - 7*x^4 + 2*x^3 + 2*x^2 + 2*x + 2)/((x - 1)*(10*x^9 - 1)). (End)
a(n) = 5 * A077492(n). - Alois P. Heinz, Sep 15 2020
MATHEMATICA
t={}; Do[i=5; While[Total[IntegerDigits[i]]!=n, i=i+5]; AppendTo[t, i], {n, 46}]; t (* Jayanta Basu, May 19 2013 *)
With[{f=5*Range[200000]}, Flatten[Table[Select[f, Total[IntegerDigits[#]] == n&, 1], {n, 50}]]] (* Harvey P. Dale, Dec 31 2013 *)
PROG
(PARI) A069534(n)=(((n+4)%9+1)*10^((n+4)\9)-5)*10^(n<5) \\ M. F. Hasler, Sep 16 2016
CROSSREFS
KEYWORD
base,nonn,easy
AUTHOR
Amarnath Murthy, Apr 01 2002
EXTENSIONS
More terms from Ray Chandler, Jul 28 2003
STATUS
approved