login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A099653 a(n) is the number of n-subsets (n=1,2,...,10) of the 10 decimal digits from which prime numbers can be constructed including all n distinct digits either with or without repetitions; a(n) <= binomial(10,n). 4

%I #20 Jul 25 2017 02:40:29

%S 5,24,96,194,246,209,120,45,10,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,

%T 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,

%U 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0

%N a(n) is the number of n-subsets (n=1,2,...,10) of the 10 decimal digits from which prime numbers can be constructed including all n distinct digits either with or without repetitions; a(n) <= binomial(10,n).

%F a(n) = binomial(10,n) - binomial(6,n) - binomial(4,n); number of n-digit subsets minus "antiprime-digit subclasses" selected from {0, 2, 4, 5, 6, 8} and {0, 3, 6, 9} digit collections.

%e n=1: {11,2,3,5,7} represent the 1-subsets; a(1) = 5;

%e n=2: A099651 includes least terms of each a(2) = 24 subsets;

%e n=5: a(5) = binomial(10,5) - binomial(6,5) - binomial(4,5) = 210 - 6 - 0 = 246;

%e n=6: each of the 6-subsets is good for primes except {0,2,4,5,6,8} so a(6) = 210 - 1.

%e n=7,8,9,10: a(n) = binomial(10,n).

%e Total number of relevant subset classes from the 1023 nonempty k-digit subsets equals 950. See also A099654.

%t Table[5 Boole[n == 1] + Binomial[10, n] - Binomial[6, n] - Binomial[4, n], {n, 83}] (* _Michael De Vlieger_, Jul 24 2017 *)

%Y Cf. A099651, A099654, A099756.

%K base,nonn

%O 1,1

%A _Labos Elemer_, Nov 15 2004

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified April 18 09:35 EDT 2024. Contains 371779 sequences. (Running on oeis4.)