Number of happy numbers without zeros and with digits in nondecreasing order <= 10^n.

Terms

a(0) =1a(1) =2a(2) =10a(3) =30a(4) =111a(5) =296a(6) =711a(7) =1625a(8) =3583a(9) =7088a(10) =13377a(11) =24143a(12) =41376a(13) =68551a(14) =111068a(15) =174887a(16) =269592a(17) =410043a(18) =612350a(19) =900484a(20) =1310108a(21) =1879862a(22) =2664399a(23) =3740002a(24) =5188376a(25) =7121305a(26) =9687674a(27) =13044961a(28) =17402217a(29) =23026128