A102041 a(n) = a(n-1) + last digit of a(n-1), starting at 7.

7, 14, 18, 26, 32, 34, 38, 46, 52, 54, 58, 66, 72, 74, 78, 86, 92, 94, 98, 106, 112, 114, 118, 126, 132, 134, 138, 146, 152, 154, 158, 166, 172, 174, 178, 186, 192, 194, 198, 206, 212, 214, 218, 226, 232, 234, 238, 246, 252, 254, 258, 266, 272, 274, 278, 286

Offset

1,1

Links

Colin Barker, Table of n, a(n) for n = 1..1000

Index entries for linear recurrences with constant coefficients, signature (2,-2,2,-1).

Formula

From Colin Barker, Oct 19 2015: (Start)

a(n) = 5+(1/2+i)*(-i)^n+(1/2-i)*i^n+5*n for n>1, where i = sqrt(-1).

G.f.: -x*(5*x^4-4*x^3-4*x^2-7) / ((x-1)^2*(x^2+1)).

(End)

a(n) = 2*a(n-1) - 2*a(n-2) + 2*a(n-3) - a(n-4). - Wesley Ivan Hurt, Apr 17 2023

Example

32+2=34, 34+4=38.

Mathematica

NestList[#+Mod[#, 10]&, 7, 60] (* Harvey P. Dale, Oct 16 2023 *)

Prog

(PARI) a=[7, 14, 18, 26, 32]; a=concat(a, vector(50)); for(n=6, #a, a[n]=2*a[n-1]-2*a[n-2]+2*a[n-3]-a[n-4]); a \\ Charles R Greathouse IV, Oct 03 2011
(PARI) a(n) = if(n==1, 7, 5+(1/2+I)*(-I)^n+(1/2-I)*I^n+5*n) \\ Colin Barker, Oct 19 2015
(PARI) Vec(-x*(5*x^4-4*x^3-4*x^2-7)/((x-1)^2*(x^2+1)) + O(x^100)) \\ Colin Barker, Oct 19 2015

Crossrefs

Sequence in context: A131439 A213604 A374004 * A232488 A351063 A070792

Adjacent sequences: A102038 A102039 A102040 * A102042 A102043 A102044

Keyword

nonn,base,easy

Author

Samantha Stones (devilsdaughter2000(AT)hotmail.com), Dec 25 2004

Status

approved