A254338 Initial digits of A254143 in decimal representation.

1, 4, 7, 1, 2, 3, 3, 4, 6, 1, 1, 2, 2, 2, 3, 3, 3, 4, 6, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 4, 4, 6, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 4, 4, 6, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2

Offset

1,2

Comments

a(n) = A000030(A254143(n));

also initial digits of A254323: a(n) = A000030(A254323(n)).

all terms are of the form u*v mod 10, where u <= v and belonging to {1,3,4,6,7}, the distinct elements of A254397:

length of k-th run of consecutive 1s = A005993(k-2), k > 1;

length of k-th run of consecutive 2s = k*(k+1)/2 = A000217(k), k >= 1;

length of k-th run of consecutive 3s = k+1, k >= 1;

length of k-th run of consecutive 4s = A065033(k-1);

n with a(n) = 4: A237424(n) = (10^a+10^b+1)/3 with b = 0, see also A093137, A133384;

n with a(n) = 6: A237424(n) = (10^a+10^b+1)/3 with a = b; A005994(a(n)) = 6 for n > 1; see also A199682;

Links

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

Prog

(Haskell)
a254338 = a000030 . a254143
(PARI) listA237424(lim)=my(v=List(), a, t); while(1, for(b=0, a, t=(10^a+10^b+1)/3; if(t>lim, return(Set(v))); listput(v, t)); a++)
do(lim)=my(v=List(), u=listA237424(lim), t); for(i=1, #u, for(j=1, i, t=u[i]*u[j]; if(t>lim, break); listput(v, t))); apply(n->digits(n)[1], Set(v)) \\ Charles R Greathouse IV, May 13 2015

Crossrefs

Cf. A254143, A254323, A000030, A254339, A005993, A000217, A065033.

Sequence in context: A367608 A021959 A188735 * A197723 A186191 A256507

Adjacent sequences: A254335 A254336 A254337 * A254339 A254340 A254341

Keyword

nonn,base

Author

Reinhard Zumkeller, Feb 27 2015

Status

approved