A125575 Initial digit of squares of primes.

4, 9, 2, 4, 1, 1, 2, 3, 5, 8, 9, 1, 1, 1, 2, 2, 3, 3, 4, 5, 5, 6, 6, 7, 9, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 4, 4, 5, 5, 5, 5, 5, 6, 6, 6, 7, 7, 7, 7, 8, 8, 9, 9, 9, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2

Offset

1,1

Links

Table of n, a(n) for n=1..100.

Formula

a(n) = A000030(A000290(A000040(n))). - R. J. Mathar, Jan 07 2007

a(n) = A000030(A001248(n)). - Michel Marcus, Aug 13 2015

Maple

A000030 := proc(n) local idig ; idig := n ; while idig > 9 do idig := iquo(idig, 10) ; od ; RETURN(idig) ; end ; A000040 := proc(n) ithprime(n) ; end; A125575 := proc(n) A000030(A000040(n)^2) ; end; for n from 1 to 100 do printf("%d, ", A125575(n)) ; end; # R. J. Mathar, Jan 07 2007

Mathematica

Table[First[IntegerDigits[Prime[n]^2]], {n, 1, 100}] (* Vincenzo Librandi, Aug 13 2015 *)

Prog

(PARI) first(m)=my(v=vector(m, i, digits(prime(i)^2)[1])); v; /* Anders Hellström, Aug 12 2015 */
(Magma) [Intseq(p^2)[#Intseq(p^2)]: p in PrimesUpTo(500)]; // Vincenzo Librandi, Aug 13 2015

Crossrefs

Cf. A000030, A000040, A000290, A001248.

Sequence in context: A098174 A126709 A254159 * A199725 A349274 A021071

Adjacent sequences: A125572 A125573 A125574 * A125576 A125577 A125578

Keyword

easy,nonn,base

Author

Anonymous, Jan 03 2007

Extensions

More terms from R. J. Mathar, Jan 07 2007

Status

approved