A154534 - OEIS

A154534

Odd nonprimes n with smallest digit of n + number of smallest digits of n = odd nonprime.

77, 105, 201, 203, 205, 207, 209, 301, 303, 305, 309, 403, 405, 407, 501, 505, 507, 603, 605, 609, 703, 705, 707, 779, 801, 803, 805, 807, 899, 901, 903, 905, 909, 989, 1011, 1015, 1017, 1023, 1025, 1027, 1029, 1035, 1037, 1041, 1043, 1045, 1047, 1053, 1055

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..1000

EXAMPLE

If n=77=odd nonprime, 7=7 and 7+2=9=odd nonprime, thus 77 is in the sequence. If n=105=odd nonprime, 0<1<5 and 0+1=1=odd nonprime, thus 105 is in the sequence.

MAPLE

filter:= proc(n) local L, m, q;

if isprime(n) then return false fi;

L:= convert(n, base, 10);

m:= min(L);

q:= m + numboccur(L, m);

q::odd and not isprime(q)

end proc:

select(filter, [seq(2*i+1, i=0..1000)]); # Robert Israel, Apr 15 2015

CROSSREFS

Cf. A141468.

Sequence in context: A247682 A127335 A193570 * A235867 A274967 A229826