A270346 a(n) is the number whose base-11 digits are, in order, the first n terms of the simple periodic sequence: repeat 2,3,5,7.

2, 25, 280, 3087, 33959, 373552, 4109077, 45199854, 497198396, 5469182359, 60161005954, 661771065501, 7279481720513, 80074298925646, 880817288182111, 9688990170003228, 106578891870035510, 1172367810570390613, 12896045916274296748, 141856505079017264235

Offset

1,1

Comments

The periodic sequence comprises the first four primes, and the selected base is the fifth prime.

Links

Table of n, a(n) for n=1..20.

Index entries for linear recurrences with constant coefficients, signature (11,0,0,1,-11).

Formula

a(1)=2, a(2)=25, a(3)=280, a(4)=3087, a(5)=33959, a(n) = 11*a(n-1) + a(n-4) - 11*a(n-5). - Harvey P. Dale, Mar 15 2016

G.f.: x*(2+3*x+5*x^2+7*x^3) / ((1-x)*(1+x)*(1-11*x)*(1+x^2)). - Colin Barker, Jul 31 2016

Example

a(8) = 45199854 = 23572357_11.

Mathematica

Table[FromDigits[PadRight[{}, n, {2, 3, 5, 7}], 11], {n, 30}] (* or *) LinearRecurrence[{11, 0, 0, 1, -11}, {2, 25, 280, 3087, 33959}, 31]

Prog

(PARI) a(n) = (-2074+305*(-1)^n+(370+410*I)*(-I)^n+(370-410*I)*I^n+1029*11^n)/4880 \\ Colin Barker, Jul 31 2016
(PARI) Vec(x*(2+3*x+5*x^2+7*x^3)/((1-x)*(1+x)*(1-11*x)*(1+x^2)) + O(x^30)) \\ Colin Barker, Jul 31 2016
(Magma) R<x>:=PowerSeriesRing(Integers(), 30); Coefficients(R!( x*(2+3*x+5*x^2+7*x^3)/((1-x^4)*(1-11*x)) )); // G. C. Greubel, Jul 14 2019
(Sage) a=(x*(2+3*x+5*x^2+7*x^3)/((1-x^4)*(1-11*x))).series(x, 30).coefficients(x, sparse=False); a[1:] # G. C. Greubel, Jul 14 2019
(GAP) a:=[2, 25, 280, 3087, 33959];; for n in [6..30] do a[n]:=11*a[n-1]+a[n-4]-11*a[n-5]; od; a; # G. C. Greubel, Jul 14 2019

Crossrefs

Cf. A033113.

Sequence in context: A174970 A249893 A085830 * A367506 A212022 A198710

Adjacent sequences: A270343 A270344 A270345 * A270347 A270348 A270349

Keyword

nonn,easy,base

Author

Harvey P. Dale, Mar 15 2016

Status

approved