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A262254 a(1) = 11; for n>1, a(n) is the smallest prime that starts with the least significant digit of the previous term and has not occurred earlier. 1
11, 13, 31, 17, 71, 19, 97, 73, 37, 79, 907, 701, 101, 103, 307, 709, 911, 107, 719, 919, 929, 937, 727, 733, 311, 109, 941, 113, 313, 317, 739, 947, 743, 331, 127, 751, 131, 137, 757, 761, 139, 953, 337, 769, 967, 773, 347, 787, 797, 7001, 149, 971, 151, 157, 7013, 349, 977, 7019, 983 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

This sequence is different from A089755, as this one does not include single-digit primes.

This sequence is different from A089755, for which a(n+1) uses all the digit of a(n) except the most-significant digit of a(n).

In this sequence, a(n+1) uses only the least-significant digit of a(n).

LINKS

Maghraoui Abdelkader, Table of n, a(n) for n = 1..200

EXAMPLE

a(3) = 31 where the most significant digit of 31 is 3, which is the least significant digit of a(2) = 13.

MATHEMATICA

f[s_List] := Block[{lsd = Mod[s[[-1]], 10], p = 3}, While[ IntegerDigits[p][[1]] != lsd || MemberQ[s, p], p = NextPrime@ p]; Append[s, p]]; s = {11}; s = Nest[f, s, 70] (* Robert G. Wilson v, Sep 16 2015 *)

PROG

(PARI) msd(n)=(n\10^(#Str(n)-1)); l1=1; l3=1; l7=1; l9=1; q=1; lsd(n)=n%10;

t1 = vector(200); i=1; forprime(n=11, 10000, if( digits(n)[1]==1, t1[i]=n; i=i+1 ; )) ;

t3 = vector(130); i=1; forprime(n=31, 3900 ,  if( digits(n)[1]==3, t3[i]=n; i=i+1 ; ));

t7 = vector(130); i=1; forprime(n=71, 70000, if( digits(n)[1]==7, t7[i]=n; i=i+1 ; )) ;

t9 = vector(130); i=1; forprime(n=97, 90000, if( digits(n)[1]==9, t9[i]=n; i=i+1 ; )) ; lsd(n)=n%10;

t = vector(200);

findnextnumber(m) =

{if(lsd(m)==1, l1=t1[i1] ; i1=i1+1; return(l1); ); if(lsd(m)==3, l3=t3[i3];  i3=i3+1 ; return(l3); );

if(lsd(m)==7, l7=t7[i7] ; i7=i7+1; return(l7); ); if(lsd(m)==9, l9=t9[i9];  i9=i9+1; return(l9); ); }

i1=1;  i3=1;  i7=1;  i9=1;  j=1; s=11;   for(n=1, 200,   p=findnextnumber(s) ; t[j]=p; s=p; j++); for(i=1, 200, print1(t[i], ", ") )

CROSSREFS

Cf. A076653, A082238, A089755, A107809, A180022.

Sequence in context: A056251 A222805 A089755 * A082238 A179551 A054262

Adjacent sequences:  A262251 A262252 A262253 * A262255 A262256 A262257

KEYWORD

nonn,base

AUTHOR

Maghraoui Abdelkader, Sep 16 2015

STATUS

approved

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Last modified July 29 13:00 EDT 2021. Contains 346346 sequences. (Running on oeis4.)